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TAC Imaging / image test.
« Last post by John Pierce on November 07, 2017, 11:55:33 PM »
this is a test, only a test.  someone reported problems uploading images here.   I present a crappy crescent moon, probably shot with a DSLR at prime focus of a C80 (Vixen 80mm achromat) about 5 years ago...

Equipment Discussions / Re: Mirror cell design question.
« Last post by Don Pensack on November 06, 2017, 02:55:17 PM »
PLOP optimizes a 3-point cell for contacts at 40% of the radius from center, so the 3 points would have to be fairly close in (1.2" from center of mirror).
The 6-point design is a bit more forgiving.  For a 6" mirror (likely 1" thick or less), you could also simply cement it to a triangular plate.
But under no circumstances would you want a spring to press directly on the mirror or even on a pad the mirror sits on.
And keep the 3 collimation springs--don't use 6.

If you experiment with PLOP, you'll find there is a point where increasing the number of points of support makes almost no difference.
With my thin 12.5" mirror, that point was with 18 points of support (which is what the mirror has).  If you put in the details and get a significant reduction in error
with a change from 3 to 6 points, use 6.  Obviously, you designed just such a cell.  My only comment there would be that you need to significantly reduce the size of the contact patches unless the cell is used on an equatorial mount.  If used on a dob/alt-az scope, the contact points could be reduced to maybe 1/4" diameter.
Observing Reports / Re: Some recent ! and !! doubles, and a question
« Last post by Dave Ittner on November 01, 2017, 04:14:16 PM »
and by the way, he meant to type
Observing Reports / Re: Some recent ! and !! doubles, and a question
« Last post by Dave Ittner on November 01, 2017, 04:12:06 PM »
Let me know when you get your encoders installed (if you can - get the 311K tic ones) and I will loan you my Nexus DSC.
It really is made for visual observers. Serge has a ton of catalogs installed that cover all of the faint fuzzies.
Observing Reports / Re: Some recent ! and !! doubles, and a question
« Last post by mccarthymark on November 01, 2017, 11:06:40 AM »
When observing at home I'm usually looking at doubles, sometimes the moon or planets.  On nights of average seeing, I use the Cambridge Double Star Atlas (2nd edition), which is a good fit for small to medium size scopes -- though there are a fair amount of challenging objects plotted too.

For nights of better seeing, I've been using the Carro Catalog of Double Stars to prepare a target list.  It was created by Joseph Carro, a southern CA observer, and published a few years ago in The Journal of Double Star Observers (, Vol. 9 No. 3 July 1, 2013, p 203-6).  Carro took the WDS and other sources, created an excel file of pairs with the A star magnitude 12 or brighter, and sorted them by constellation.  When I found the list a couple years ago JDSO had a link to the spreadsheet on its home page, but I don't find it there now.  If anyone wants a copy PM me and I'll email it to you.  I've seen other spreadsheets based on the entire WDS, but without the constellation names they were too time-consuming to use for session planning.

12th mag is about the limit of my 12.5-inch scope from a red-zone location.  To prepare I check if the object is plotted in CDSA; if it isn't then I consider if it is doable, then prepare a finder chart using AAVSO's VSP (  I print those out and sort the pages in a logical star hop sequence, so when I have a good night I get up on the ladder and start searching for each one; often I don't have to come down from the ladder until I have to reset my equatorial platform--there's usually quite a lot of targets to search for.

I'm thinking of getting Nexus DSC which, per the manufacturer, will have all the Struve and ADS catalogs included in the database in their next firmware release.  This would unlock many more targets.

** edit: corrected URL & some grammar; thanks Dave
Observing Reports / Re: Some recent ! and !! doubles, and a question
« Last post by sgottlieb on October 31, 2017, 06:25:43 PM »
I really enjoyed reading your results, Mark!  You've really taken on the challenge of close, unequal doubles.  Great job!!

Are these doubles you ran across using the Interstellarum Deep Sky Atlas or from another source?
Observing Reports / Re: Dinosaur Point Saturday night, 21 October
« Last post by DDK on October 31, 2017, 02:20:06 AM »
We negotiate those exit times on site. I'm not promising anyone will be opening the gate at 11 pm. And 2-3 parades could quickly get to be too many. As said, we can figure it out in the lot there that night. It's not an SCAC event up front.
Observing Reports / Re: Dinosaur Point Saturday night, 21 October
« Last post by John Pierce on October 30, 2017, 10:48:37 PM »
awesome, ok.     i'm asking the club if they wanna do this.     I'm suggesting 2-3 scheduled exit windows, maybe 11pm for the wimps, 1am and I dunno, 3am ?   give folks a 30 minute reminder that if they wanna go its now or hours later...   its only 1:15 drive from central s'cruz.

if you post a dec 16 OI, I'll move this discussion over there...
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Observing Reports / Re: Dinosaur Point Saturday night, 21 October
« Last post by DDK on October 30, 2017, 03:14:18 PM »
Yes of course we work on accomodating people. Yes we do exit parades. And no we do not hold stargazers hostage behind a locked gate till dawn.
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