From: Rodolphe Pineau <pineau@rti-zone.org>

Date: June 4, 2012 8:41:06 AM MDT

To: Astro_IIDC@yahoogroups.com

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

On Mon 6/4/12, at 1:23, Albert Ros wrote:

Hi Rodolphe ,

Are you using an IR/UV block filter ? you are non mention it in your set up .

I am not using an IR/UV block filter (I have one ordered but it will not be here in time for the venus transit).

Since your telescope is an achromat it could be the chromatic abberation that spoils the image .

I though about this too and that's why I also did some test with my SN8 which is a reflector and I saw the same problem.

As Stephen said at this point it's either the filter or as you suggest so IR or UV blurring the picture as the CCD sensor is sensitive to IR (I'm not sure about UV).

Regards

Albert

Thanks for your reply.

Rodolphe

On Jun 4, 2012, at 2:50 AM, 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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