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Astro Camera for solar imaging through a PST

sologuitarist61

By sologuitarist61
in Discussions - Cameras

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sologuitarist61

sologuitarist61

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Let me say up front that I know very little about astro cameras or how to use them.

Up until now I have been using my Canon 50d for all my solar imaging and that is fine for white light, but I am having difficulty using my PST as the view through the camera is very dim, and focus/detail hard to make out. I could of course put the Canon through Backyard EOS, but am thinking to save weight on such a small scope as the PST (or indeed on the focuser of my other refractors)..

Now one thing I have noticed about astro cameras is that they all seem to have very small chips compared to the APSC sensor on the Canon and hardly any pixels (sorry but I am used to 16MP). Not being a great one for stitching bits together in CS6 I was wondering if there is anything out there that would still allow me to get the full solar disk in one go. Don't particularly want a colour chip, mono will be OK and I will needto be able to use it later for DSO's as well.

Can afford about £600 at a push - any ideas?

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sologuitarist61

sologuitarist61

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Because the back focus of the PST is very short it is necessary to use the lens element from a Barlow (1.5 or 2 x) to get sharp focus. This works with my all my Canon dSLRs.

canon_450d+2x_barlow.jpg

pst_solar_02.jpg

Thanks for that, but trying to get away from using the Canon as the view is so dim.

Alexandra uses the DMK41 as far as I recall. Hence my interest in the one on ebay at the weekend.

James

Yes I noticed that James and have read up on it, however I am unsure as to whether this will give full disk coverage or whether stitching will still be required.

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JamesF

JamesF

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Yes I noticed that James and have read up on it, however I am unsure as to whether this will give full disk coverage or whether stitching will still be required.

You're not getting a full disc with the DSLR, are you? If not I think you certainly won't with the DMK.

James

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RikM

RikM

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A DMK41 on a PST should get the whole disc in but sometimes they don't quite come to focus so you need to use a barlow element and then the whole disc wont fit. I am not sure why some will reach focus and other won't though? It is something more peculiar than just using the correct nosepiece.

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Montana

Montana

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Hi Richard,

I get this a lot, I do not stitch anything together with the PST's. All are a one shot at prime focus, both the CaK PST and the Halpha PST are identical in every way. Here is a picture not cropped at all to show the field with a DMK41 through a PST at prime focus

8192249911_c61aae043d_c.jpg

2012-11-10 12-54-18 DMK41 image scale by Alexandra's Astronomy, on Flickr

and I use this nose piece to do it

8192234953_6956a68fc4_c.jpg

Short nose piece on DMK41 by Alexandra's Astronomy, on Flickr

bought for £19 from Modern Astronomy (first item under the 'Accessories for Astrovideo cameras' it seems to work for everyone who has tried it so far. Carbon60 bought one last week and it worked for him too.

http://www.modernastronomy.com/camerasAstroVideo.html#mintron12v

I am not sure how well a DMK41 performs on DSO's though as I have never tried.

Kind regards

Alexandra

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GlassWalker

GlassWalker

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I'd echo that, when used at prime focus on PST, the DMK41 allows the full sun to fit with room to spare. The focus question is an odd one, and neither of my two PSTs (both regular Ha versions of different ages) can prime focus with the DMK41 even with the short nosepiece. On one PST I've shaved the eyepiece holder to give the extra room and that works great now.

When I started, I also wanted to do a full sun in one go. Having had to use the barlow trick previously to get focus, it is clear that gives noticeably more detail so you may want to try that too!

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michael.h.f.wilkinson

michael.h.f.wilkinson

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I am looking for something like that for my little Lunt LS35THa. My webcam will not come to focus, but maybe the DMK41 will. If not, it should do so by replacing the helical focuser with this one:

http://www.teleskop-express.de/shop/product_info.php/language/en/info/p4591_Borg-T2-Helikal-Auszug---kurzbauend---Kamera-dreht-nicht-mit.html

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sologuitarist61

sologuitarist61

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I'd echo that, when used at prime focus on PST, the DMK41 allows the full sun to fit with room to spare. The focus question is an odd one, and neither of my two PSTs (both regular Ha versions of different ages) can prime focus with the DMK41 even with the short nosepiece. On one PST I've shaved the eyepiece holder to give the extra room and that works great now.

When I started, I also wanted to do a full sun in one go. Having had to use the barlow trick previously to get focus, it is clear that gives noticeably more detail so you may want to try that too!

When you say you 'shaved off' the eyepiece holder, I assume you mean on the PST - did you have to take much off? The only reason I ask is that I don't want to shell out on a DMK41 and then find it doesn't work with my PST - so am exploring all the options. Could you also have filed down the short nospiece for the same outcome? :huh:

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JamesF

JamesF

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When you say you 'shaved off' the eyepiece holder, I assume you mean on the PST - did you have to take much off? The only reason I ask is that I don't want to shell out on a DMK41 and then find it doesn't work with my PST - so am exploring all the options. Could you also have filed down the short nospiece for the same outcome? :huh:

Could be that the eyepiece holder is too long to allow the DMK sensor to reach the focal plane even when it's flush with the case of the camera. It wouldn't matter what you did with the camera nosepiece in that situation. You'd have no option but to shorten the eyepiece holder.

Is the eyepiece holder removable? If so, perhaps rather than butchering the original it might be possible to get a shorter replacement made?

James

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sologuitarist61

sologuitarist61

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Could be that the eyepiece holder is too long to allow the DMK sensor to reach the focal plane even when it's flush with the case of the camera. It wouldn't matter what you did with the camera nosepiece in that situation. You'd have no option but to shorten the eyepiece holder.

Is the eyepiece holder removable? If so, perhaps rather than butchering the original it might be possible to get a shorter replacement made?

James

Thanks for that James I understand the point now :laugh:

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GlassWalker

GlassWalker

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The short nosepiece allows the DMK to get as physically as close to the PST as is possible. The eyepiece holder needs to be shortened further in my case, and I know I'm not alone, but certainly it doesn't affect every PST either. You can unscrew the eyepiece holder assembly, but there's two filters in it you need to keep and it isn't so fun to break that down further. Can't remember how much I removed, but it was several mm, which now gives it plenty of room to focus.

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Merlin66

Merlin66

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Rik,

There are only two variables in the equation:

1. The actual focal length of the rear lens at the etalon - this should, by design be 200mm

2. The size and position of the pentaprism on the adjusting arm- this moves to provide the focus on the PST - it maybe that the size or travel varies slightly....

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sologuitarist61

sologuitarist61

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The short nosepiece allows the DMK to get as physically as close to the PST as is possible. The eyepiece holder needs to be shortened further in my case, and I know I'm not alone, but certainly it doesn't affect every PST either. You can unscrew the eyepiece holder assembly, but there's two filters in it you need to keep and it isn't so fun to break that down further. Can't remember how much I removed, but it was several mm, which now gives it plenty of room to focus.

Many thanks for that information - I just might need it!! :grin:

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