31 December 2011

The forecast said the clouds would dissipate enough at 1900 to get a bit of Jupiter and the First Quarter Moon so I headed up to TotL with the Mini Mak to see the fireworks. It didn't look like I was going to see anything but the fireworks while I was walking up there but by the time I arrived it was clear although not many stars were visible due to the haze.

It took me 30 minutes to get the Orion EZFinder Deluxe realigned with the Mini Mak after having last used it on the mortar. Later in the evening I found that it was off when sighting objects low in the W. I sighted in on a nearby lamp post then refined my settings on the top of a distant building. Until now I have been using the circle with dot reticle but think I like the circle over crosshairs better. I tried doing a drift test to confirm that the circle is 1° but have not done the calculations on it yet.

Just before the fireworks started I got Mars through the trees in Manhattan NE.

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Exoplanets

Nearly twice as many exoplanets were discovered this year than last year (196 vs 108) and over 1/4 (27.37%) of all known exoplanets were discovered this year.

The rate of discovery has continued to accelerate.

Taking a longer view nearly half (41%) as many exoplanets have been discovered in the first year of this decade (2011-2020; 196 exoplanets) as in all of the prior decade (2000-2010; 471 exoplanets).

Of the known exoplanets, 149 (20%) are within the habitable zone of their exosun and 223 (31%) are members of multi-exoplanets systems.

Method of discovery:

Method	Discoveries
Radial Velocity	457
Transiting	200
Microlensing	14
Direct Imaging	28
Eyeball Observation	0

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Observing Hours for the Year 2011

	Day			Night			Total
	Hours	Days	Avg	Hours	Days	Avg	Hours	Days	Avg
Jan	0.00	0	0.00	2.00	1	2.00	2.00	1	2.00
Feb	0.00	0	0.00	2.00	1	2.00	2.00	1	2.00
Mar	0.00	0	0.00	7.00	3	2.33	7.00	3	2.33
Apr	0.00	0	0.00	8.25	2	4.13	8.25	2	4.13
May	1.25	3	0.42	16.00	5	3.20	17.25	7	2.46
Jun	0.00	0	0.00	4.00	1	4.00	4.00	1	4.00
Jul	3.50	4	0.88	14.00	5	2.80	17.50	8	2.19
Aug	2.75	7	0.39	6.50	2	3.25	9.25	8	1.16
Sep	0.50	1	0.50	4.50	1	4.50	5.00	2	2.50
Oct	3.50	4	0.88	11.50	4	2.88	15.00	7	2.14
Nov	6.50	5	1.30	13.75	5	2.75	20.25	9	2.25
Dec	2.00	3	0.67	26.50	6	4.42	28.50	6	4.75
TOTAL	20.00	27	0.74	116.00	36	3.22	136.00	55	2.47

                       

26 December 2011

Peter and I met this afternoon to discuss observing options for the coming week. The forecast for the NE doesn't support 12-16 hours of driving plus expenses to get to a dark sky site so we opted for ad hoc "local" trips as weather permits. The first trip was tonight to Custer Institute in Southold, Long Island.

The sky was clear most of the night with a few stripes of cloud invading on the horizon. Around 0400 it started to get a bit hazy but that was when we were planning to pack it in anyway.

I took the mortar out. In preparation for the big trip I had mounted a shoe on it dor the Orion EZFinder Deluxe and had taken it out during the week to try to zero it in. The finder is off by about a degree when the adjustment screws are at their limit. That gets the target star very close to the field stop of my 2" Orion 38mm Q70 eyepiece so can be dealt with but at some point I might try some adjustment of the shoe if the epoxy will permit it. I would like it to me as nearly in agreement with the settings for the Mini Mak as possible so I don't have to spend my night trying to align it with the scope. But when I was packing up I forgot to throw in the box the finders live in so had to do all my locating sighting over the centerline of the clamshell.

The Q70 performed well for me tonight. The FoV isn't perfectly flat but it compares well with Peter's much more expensive Pentax eyepiece of similar specifications. It gives me a much more familiar FoV to use for star hopping which is what I bought it for. As far as observing goes it will hold all of Otion's Sword or the Pleiades.

We played a bit with our UHC and Broadband (I think that is what he has) filters. We looked at the Pleiades and could see a glow around all the stars. Custer is where I first saw nebulosity there. I had often seen a glow before but had always attributed it to bright stars lighting up atmosphere. I panned around the sky and found that almost any random star I landed on and other bright stars that are not noted as being in nebulous regions exhibited a nebulous glow so we don't know how much of what we were seeing in M45 was real nebulosity and how much was atmosphere.

As expected, most of my time was spent just looking naked eye. I would have liked to have stretched out on the grass and spent time watching the stars wheel overhead but it was too wet for that. When I got home I found that my kneepad and the feet of my observing chair were covered with mud so I am glad I didn't try. My scope and eyepiece got covered in frost as did the filter on the front of Peter's Camera. I put the cap on the eyepiece and after a while the frost was gone. I guess I should dig that lens out and check on it's condition. Peter is going to supply plans for a DIY eyepiece heater.

Some meteors were spotted but the most interesting site was Jupiter. I knew I was seeing two moons right next to each other and thought there was a third one there which I confirmed in SkySafari. We often see two moons together and sometimes two pairs of close moons, but have never seen three moons lined up before.

Peter saw a few objects that he has rarely seen before and I got a look at some of them in his scope.

I performed another drift test tonight. Peter said one of the belt stars was on the celestial equator but he couldn't remember which one so I used Alnilam rather than getting the iPad out and checking to see which star I should be using. I figured it it wasn't the right star I would only be off by one star and the correction wouldn't be horrendous.

My spreadsheet is not working properly. Now my answer is too far from the values I have previously calclated. I have reworked the sheet breaking the formula down into components to try and debug it but I can't see what I have done wrong. And I am still having the issue of it returning the right value but in the wrong direction (eg. a FoV_T of -3.8).

24 December 2011

I went up to TotL tonight with the mortar (my dobsonian). I have attached a shoe to the front end for my Orion EXFinder Deluxe and I wanted to get it zeroed in before out big dark sky observing trip.

I set the shoe on the Sonotube and let it align itself with the curvature of the tube. Then I held it in place and drilled one of the screw holes. After inserting a screw I tried to get the shoe lined up again with the curvature and drilled the second hole. The first thing I found was that they largest drill bit I have for my Dremel is smaller than the screws I have to hold it in place. The shoe came with screws that would have fit through my hole but they were too short to reach all the way through the tube and allow a nut to be screwed on. So I had to screw the screws through the cardboard to enlarge the holes. This might have caused some drift of either or both of the holes. Peter down at Adorama said to be sure to seal the holes with epoxy and use washers on the inside so I did that. The epoxy wasn't flowing through the holes so I had to drive the screws through it before it set up. This got epoxy in the threads which is likely binding them to the cardboard. And I had to put the nuts on before epoxy in the threads hardened and prevented me from doing that so they might be epoxied to the screws.

And when I started to zero the finder in I found that where it was set for the Mini Mak was way off from where it needs to be for the mortar. I cranked the screws as far as they would go and got it within about 0.5° in altitude and about 1° in azimuth. with the 2", 38mm Orion Q70 finder eyepiece the target object is very close to the field stop so it will be usable but I would like to get it better aligned it I can break the right screw free and drift that hole a little bit.

I made a drift test with the Q70 to see how big its field of view is. I looked up FoV_T in Astronomy Hacks and have created a spreadsheet to do the calculations for each of the three methods they describe.

They say that calculating FoV_T based on the eyepiece magnification and FoV_A is the least accurate method, especially when dealing with inexpensive Chinese eyepieces and telescopes, due to variations in focal length from item to item. My eyepiece is definitely an inexpensive Chinese on and the telescope focal length I am using to calculate the eyepiece magnification is my best guess for a physical measurement without scratching my mirrors so there is definitely slop in there. I come up with FoV_T = 3.6°.

Basing the calculations on the eyepiece field stop is supposed to be more accurate so I looked that up on the Orion web site and made my calculations by that method and come up with FoV_T = 3.5°. I would imaging that if there are manufacturing variations in the focal length of inexpensive optics the same would hold true for the diameter of the field stop so don't hold this number to be gospel either.

The gold standard for determining FoV_T is supposed to be the drift test. It is recommended that the star used for the drift test be as close to the celestial equator as possible. It should also be southing at the time of the test so it is moving horizontally across the sky. Finding something bright enough for me to hop to it in that location didn't seem like an option so I used Jupiter and corrected for the difference in Dec. I also did a half drift test starting with Jupiter in the center of the FoV as nearly as I could judge it. I came up with FoV_T = 3.8°.

So I figure my FoV_T is somewhere in the 3.6° - 3.65° range. I should perform this test again on a star and do it several times to correct for placement of the target in the center of the FoV.

The Dec for Jupiter was positive at the time but when I uncheck the Minus box the FoV_T comes out as -3.8.

14 December 2011

It has been so long since I have actually written a blog post that it is a real reach to pull out all of the HTML to get this one done.

Peter and I were discussing the possibility of mounting a dark sky expedition between Christmas and New Years.  

First we need to decide where to go.  That is a tradeoff between how dark the sky is and the drive time to get to it.

I have previously compiled and posted a list of the darker dark sky public observing sights as listed in Clear Sky Clock but can't find it now that I need it.    I only remembered two areas of the NE that have Bortle 1/2 skies: an area in northwestern Maine and the area of West Virginia between Spruce Knob and Green Bank.  Both of these areas have some detractors.  West Virginia is 7-9 hours away, not counting breaks, and, as I remember it, the Maine site is a similar distance, is hard to get too because it is in the middle of nowhere (maybe that is why it is dark) and doesn't look like there are a lot of resources (lodging, sustenance, cell phone coverage, WI-Fi).
[I just found the Dark Sky Finder that has a copy of the Bortle map that will make it easier to do this search in the future.  I don't know what they are using for their data source but a quick look indicated some good data categories an the tabular data associated with each push pin.  And I suspect there are different sites there than on other sites.]

So I "Googled" "dark sky sites" and came up with ObservingSites.com.  Peter and I discussed some possible candidates.  He is partial to sites in western PA where the conditions are Bortle 3-3+, while I am partial to the WV sites which are Bortle 1/2-2+.

Anyway in looking at this we found a county park near Grantsville, WV, in Bortle 1/2 country, that is supposed to have impressive skies and an old barn you can stay in for cheap.  Peter will consider WV -- the difference in drive time is not that great when you consider the total drive time, and the price is right if it is available in the winter -- but is keeping his options open for PA.  While I figure if we are going to a dark sky site we should shoot for the darkest one possible I recognize that a dark sky site is wasted on me since after the sky fills up with more than our six Central Park stars I am lost and can't even find bright things like the Big W or the Big Dipper.  I am thinking mostly I will be appreciating how much we are missing in The City and trying to identify the familiar constellations.

And now I am remembering the cabin in the mountains on the margin of a Bortle 1/2-3 area where I spent weekends one semester in college.  It looks like the cabin is still there (if I am remembering the geography from 30 years ago and am correctly translating it onto Google Earth and Maps), but I don't know if my classmate's brother still owns it and would let us use it.  It is on the side of a hill so would have an obstructed western horizon and there is another hill across the valley to the west.  The area is within the Manongahela National Forest and is very rural (when I was in college you could get fresh deer meet and moonshine  there all year round).  And we could always use it as a base to access other areas like Spruce Knob and Green Bank, and for side trips to tourist attractions.

To aide and abet our selection process I looked at the historical weather information in Clear Sky Clock.  In the table beneath the chart there is sometimes a link to this data in the rightmost cell of the bottom table row.  If you look at the listing of sites within a state the locations that have this data are indicated by a red star in the first column.  There aren't many of them and, as in this case, they are probably not the site you want, but at least they give an indication of conditions this time of year around the state.  WV and PA are not looking great.

Then I remembered dry day.com, a site that predicts the likelihood of a given day being dry 18 months in advance and locks in their forecast.  They claim an 85% accuracy rate.  I have used the site numerous times but have no idea how their predictions stack up against ground truth in NYC.  So I decided to find out.  I have looked up the forecast going forward and am going to compare it with the Central Park observed conditions for the remainder of the month.  I will be looking at "average" cloud cover, humidity and precipitation recorded each calendar day

dryday.com graphic

dryday.com graphic

Date	dry day.com		Central Park	LGA
	Condition	Risk of Precipitation	Reported Conditions	Observed Conditions
15	Risky	48%	Day: O Night: MC Precip: T RH: 68%	Day: O Night: MC Precip: T RH: 66%
16	Transition	42%	Day: O Night: MC Precip: 0.00" RH: 48%	Day: MC Night: MC Precip: 0.00" RH: 48%
17	Transition	48%	Day: O Night: O Precip: 0.11" RH: 89%	Day: MC Night: MC Precip: 0.00" RH: 54%
18	Risky	58%	Day: C Night: C Precip: RH: 0.00"	Day: PC Night: PC Precip: 0.00" RH: 46%
19	Risky	50%	Day: MC Night: O Precip: 0.00" RH: 54%	Day: MC Night: O Precip: 0.00" RH: 53%
20	Transition	42%	Day: MC Night: O Precip: 0.01" RH: 64%	Day: O Night: O Precip: 0.01" RH: 62%
21	Dry	25%	Day: O Night: O Precip: 0.11" RH: 89%	Day: O Night: O Precip: 0.08" RH: 83%
22	Dry	40%	Day: PC Night: MC Precip: 0.06" RH: 60%	Day: MC Night: O Precip: 0.05" RH: 59%
23	Dry	11%	Day: O Night: C Precip: 0.75" RH: 77%	Day: MC Night: PC Precip: 0.76" RH: 72%
24	Dry	10%	Day: PC Night: C Precip: 0.00" RH: 4%	Day: PC Night: PC Precip: 0.00" RH: 52%
25	Transition	42%	Day: MC Night: PC Precip: 0.00" RH: 57%	Day: MC Night: O Precip: 0.00" RH: 55%
26	Risky	49%	Day: PC Night: C Precip: 0.00" RH: 56%	Day: PC Night: PC Precip: T RH: 52%
27	Transition	40%	Day: MC Night: O Precip: 1.02" RH: 79%	Day: O Night: O Precip: 1.17" RH: 73%
28	Dry	18%	Day: O Night: MC Precip: 0.00" RH: 59%	Day: MC Night: PC Precip: 0.00" RH: 57%
29	Transition	43%	Day: PC Night: Precip: 0.00" RH: 46%	Day: MC Night: O Precip: 0.00" RH: 43%
30	Risky	52%	Day: C Night: PC Precip: 0.00" RH: 65%	Day: MC Night: MC Precip: 0.00" RH: 61%
31	Risky	70%	Day:MC Night: C Precip: 0.01" RH: 73%	Day: MC Night: PC Precip: 0.01" RH: 73%
Legend C = Clear PC = Partly Cloudy MC = Mostly Cloudy O = Overcast

I am comparing the dryday.com assessment against the automated observations from Central Park which may not be fair. I have long felt that the instruments at the Central Park weather station are optimists. When I was out this afternoon it was overcast but Central Park reported it as clear and tonight the GOES images show clouds blanketing the area while it is supposed to be clear at Central Park. So maybe I should add another column and also compare the La Guardia Airport observations. At least there are people there who might be looking out a window and notice clouds. Then I will be able to validate the two weather stations against each other and the dryday.com forecast against them.

Converting hourly observations of the current weather to Day and Night generalizations wasn't easy. I ended up loosely defining Day as 0751 to 1751 and Night as 1851 to 2351 and kinda averaging out what was reported over the period. It was hardest when the observations ranged between Clear and Overcast. I probably should have converted the text into octas and averaged them but even that would have had a lot of slop in it since a cloud cover description can span several octas and some of them overlap in their octa values.

I looked at what condition they assigned each day relative to their predicted Risk of Precipitation.

Risk of Precipitation	Dry	Transition	Risky
90%-100%
80%-99%
70%-79%	1
60%-69%
50%-59%			3
40%-49%	1	6	3
30%-39%
20%-29%	1
10%-19%	3
0%-9%

I looked at Risk of Rain compared about actual rainfall.

Risk of Precipitation	Rain	No Rain
90%-100%
80%-89%
70%-79%	1
60%-69%
50%-59%		3
40%-49%	6	3
30%-39%
20%-29%	1
10%-19%	1	2
0%-9%

As you would expect, when they predicted a low Risk of Precipitation they also predicted that it would probably be Dry. When the Risk of Precipitation rose they said it would be a time of Transition. And when the Risk of Precipitation was very high they said it would be a Risky time to schedule outdoor activities. There appears to be about a 10% overlap between Dry and Transition and is aseumedly a similar overlap between Transition and Risky. When compared with the Risk of Precipitation vs Condition chart above I come to the conclusion that it rained about 50% of the time when they said there was a high probablility that it would and that it rained about 50% of the time when they said there was a low probablilty that it would.

Lastly I compaired when it would rain against the risk condition they assigned each day.

	Rain	No Rain
Dry	3	2
Transition	3	3
Risky	3	3

Again it looks like it didn't tain about 50% of the time when they said it would probably be dry and rained the other 50% of the time. And during the time when they said it would probably rain it rained about 50% of the time and was dry the other 50% of the time.

Based on this short assessment I don't see this forecast being much good for astronomy or for anything else other than possibly as a CYA if you have to schedule an weather dependant event well in advance. You might as well flip a coin.

Looking at the reported conditions for Central Park and LaGuardia Airport I only found one instance where their cloud cover data was more than one "unit" in difference (25Dec11: Partly Cloudy vs Overcast) so my feeling that Central Park is overly optimistic remains a feeling. I have built a mirror to take cloud cover measurements . I tried it out at Bryant Park when I was doing solar observations on 26Dec11 and found that the clouds moved so quickly that it was hard to get an accurate count. Maybe I will have better luck taking pictures of the mirror and counting the clouds that way. My plan is to count the clouds at 51 minutes past the hour at Belvedere Castle and compare my assessment with the report of the Central Park automated weather station submitted at the same time.