From: "Stephen W. Ramsden" <sramsden@natca.net>

Date: June 4, 2012 12:02:41 AM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Issues taking pictures of the Sun with a PGR Scorpion


well,

If you can focus without the filter but you cannot focus with the filter, then the filter is the problem.





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Stephen W. Ramsden

sramsden@solarastronomy.org


"Astronomy compels the soul to look upwards and leads us from this world to another"

Plato, The Republic



On Jun 3, 2012, at 8:50 PM, Rodolphe Pineau wrote:

I have a PGR Scorpion (the 1600x1200 model) and I've been trying to use it to take picture of the sun with Astro IIDC.
My problem is that I can't get a proper focus on the sun.
I'm using a ST90 with an Antares focuser, 2 2" extension tube and the PGR. The solar filter is an Identi-View from J.M.B Inc (it's an 8" filter but I built an adapter to use it with the ST90).
Here are some sample of why I get at best focus with Astro IIDC :

http://www.rti-zone.org/astro/tmp/20120603_151234_L.mov_80LN.tif
http://www.rti-zone.org/astro/tmp/20120603_151525_L.mov_80LN.tif
http://www.rti-zone.org/astro/tmp/20120603_155626_L.mov_80LN.tif

These are processed in Astro IIDC with the "Simple Solar" profile and are stack of less than 30 frame out of 700+ in each case.

I tried with other cameraa (a DFK 21F04 and a DMK 21AF04.AS) and it's the same.
As a side test I took my canon 20D, put it on the telescope, did a coarse focus (not the easiest thing using the viewfinder as this is not a Da so it doesn't have the live view for focussing) and shot a few frames. This is the best of them with minor sharpening and level in Photoshop CS4:

http://www.rti-zone.org/astro/tmp/Sun_20120603.jpg

This is a lot better than the one from the PGR.

I did some similar test with my Meade SN8 but got similar result with the PGR (and the DFK 21F04 and DMK 21AF04.AS).

http://www.rti-zone.org/astro/tmp/20120602_171454_L.mov_80LN.tif
http://www.rti-zone.org/astro/tmp/20120602_171742_L.mov_80LN.tif
http://www.rti-zone.org/astro/tmp/20120602_171921_L.mov_80LN.tif

I tried with and without a Baader Solar Continuum filter but it didn't make any difference in term of focussing and getting a crisp picture (I had to increase the exposure but all other parameters were the same).

If I point the telescope at a tree far away I can focus properly without any issues !!!

With the Venus transit in 2 days I'd like to figure this out before then .. if possible.

So if anybody has an idea of what's going on I'll be happy to hear from you !.

--

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