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Which camera for the PST?

Stu_2011

By Stu_2011
in Imaging - Solar

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Stu_2011

Stu_2011

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Good morning and happy new year!

I have dabbled with solar imaging in the past year with my PST with a colour imaging source camera that I use for planetary stuff. However, the sensor is small and colour so not really ideal for solar particularly as it seems that mine is one of the PSTs that needs a barlow to get to focus.

I'm trying to work out my best options for a bigger mono camera. Whats the current thinking about the best camera / barlow options for the PST now?

It seems to me that ideal camera for the PST would be one with a 1.25 diameter body (like the Lodestar or QHY5 II guide cameras so you could position the sensor at the correct focus point) with a 1/2" mono CCD that would do fast frame rates and was free from fringes / sensor reading defects. All these features seem to exist individually on different cameras but unless I'm wrong none seem to exist on a single camera.

Thanks

Stuart

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DrRobin

DrRobin

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DMK41 is a safe route but if your colour cam won't reach focus without a Barlow then a DMK41 will be exactly the same. You won't get a full disc in one go with a barlow and have do to mosaics but they give you a better imaging scale in any case.

I tried a Lifecam HD in a 1.25" body and it went into the holder of my PST and achieved focus without a Barlow and gave a full disc, but colour cams are no good for Ha, so if the QHY5-II is free from newton rings then it would be a good solution, they are cheaper than a DMK41.

Some people on here have used them so do a search on this section to see if anyone reported problems.

Robin

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Stu_2011

Stu_2011

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Thanks both, a DMK41 mono looks a safe bet and I don't mind doing Mosaics with a barlow.

I was just reading about this focus issue and some people have had some success in using clear glass / red / Ha filters in front of the camera sensor to extend the focus point a bit. I might try this as well as my colour camera was fairly near to focus so this might help out. Have either of you had experience with this approach?

Also, I have read some reports that the DMK41's have some issues with banding and fringes at certain frame rates, is this still the case or has a firmware update sorted out the problem?

I have plenty of time - not much sun due for a bit!

Stu

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JamesF

JamesF

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As regards the DMK41, temporarily I have a small collection of DxK cameras that I've been using to test my capture application.  They're all second hand and some of them have a "collar" that fits behind the nosepiece, but not all.  The collar looks like it is male C thread to female C thread and isn't hard to remove.  I wonder if the reason that some people have problems focusing even with a short nosepiece is because they have the collar in place, whereas others may not, effectively moving the sensor about 6mm further in?

I don't have one, but it struck me the other day that the QHY5-II might be a usable solar Ha camera with the PST as well.  It has a 1/2" sensor and the cylindrical design means it should have no problems reaching focus.  The only question is if it suffers from the "Newton's RIngs" problem that has been reported with some of the Aptina sensors.  At well less than half the price of the DMK41 it could be quite tempting if it works properly.

James

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Stu_2011

Stu_2011

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Thanks James

Yes I have one of the IS cameras with the collar but when I attach a short nose piece the collar sits inside the eyepiece tube of the PST with the body of the camera hard up against the end of the eyepiece tube. The camera wont go in any further if I took off this collar. I think some collars are wider than others on some cameras so this could be a factor.

The QHY5-II of the QHY5L-II cameras interest me due to the form factor that gets round this focus problem. It's the Newton ring uncertainty thing that bothers me. Maybe a chat with the ever helpful Bernard at Modern Astronomy might help?

Also, am I right in thinking that someone that posts on SGL was writing a capture program for the Lodestar guiders? I know that these cameras don't capture AVI's as standard but if they could that would be an attractive option. The bigger Lodestar has a 1/2" CCD in a 1.25" form factor......that COULD work well if it captured cleanly at a good frame rate.

Thanks

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JamesF

JamesF

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Thanks James

Yes I have one of the IS cameras with the collar but when I attach a short nose piece the collar sits inside the eyepiece tube of the PST with the body of the camera hard up against the end of the eyepiece tube. The camera wont go in any further if I took off this collar. I think some collars are wider than others on some cameras so this could be a factor.

The QHY5-II of the QHY5L-II cameras interest me due to the form factor that gets round this focus problem. It's the Newton ring uncertainty thing that bothers me. Maybe a chat with the ever helpful Bernard at Modern Astronomy might help?

Also, am I right in thinking that someone that posts on SGL was writing a capture program for the Lodestar guiders? I know that these cameras don't capture AVI's as standard but if they could that would be an attractive option. The bigger Lodestar has a 1/2" CCD in a 1.25" form factor......that COULD work well if it captured cleanly at a good frame rate.

The sensor on the QHY5L-II is only 1/3" I think.  The larger sensor on the QHY5-II has the advantage of getting the entire image in a single frame.  I have seen it proposed that a camera tilting mechanism be used to get rid of the rings, but I think that's pretty horrible myself.  Could well be worth chatting over with someone in the know, anyhow.

Someone was definitely working on a (Mac-based, I think) Lodestar capture application.  My searching finally found some information here:

http://stargazerslounge.com/topic/202377-lodestar-live-december-update/

I'm fairly sure mallorcasaint uses an Atik 314L+ to capture data from his PST, but I think he's done a stage 1 mod, so doesn't have the focus range problem.

James

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Montana

Montana

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This might answer some of your questions about the PST and where the length problem is http://solarchat.solarastronomy.org/index.php/en/this-is-solar-chat/24-commercial-solar-filtershardware/86969-dmk41

I have never seen banding or fringing with frame rates, mine does the full 15fps every time with no problems. With some barlows you will get Newton's rings but that is the same with all cameras as it is the nature of the etalon, just some cameras are worse than others.

Alexandra

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Stu_2011

Stu_2011

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Thanks Alexandra,

I seem to have one of the long eyepiece models as well so this could explain the focus issues.

I have three options as far as I see it

1. Take 5 mm off the eyepiece holder (I have a lathe so easy to do but I'd rather not to be honest). Can use the trusted DMK41.

2. Use a barlow and do mosaics, I don't mind this to be honest. Can use a DMK41.

3. Get a 1.25" form factor camera like the QHY5 II that will allow the sensor to sit further forward and get to focus. Little bit unproven but solves a lot of problems if it works.

Any other suggestions or comments?

Thanks again

Stuart

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JamesF

JamesF

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Thanks Alexandra,

I seem to have one of the long eyepiece models as well so this could explain the focus issues.

I have three options as far as I see it

1. Take 5 mm off the eyepiece holder (I have a lathe so easy to do but I'd rather not to be honest). Can use the trusted DMK41.

2. Use a barlow and do mosaics, I don't mind this to be honest. Can use a DMK41.

3. Get a 1.25" form factor camera like the QHY5 II that will allow the sensor to sit further forward and get to focus. Little bit unproven but solves a lot of problems if it works.

Any other suggestions or comments?

Short of turning replacement parts up rather than cutting down existing ones, or biting the bullet and doing modding the PST (which can actually be done non-destructively) I think that's a fair summary of your options.

I took the path of modding mine, replacing the focuser unit and shortening the optical path at the same time:

dovetailed.jpg

but all that is involved from the PST side is removal of the tube and the eyepiece holder from the "black box" (obviously it does now require a separate finder).  I turned up a new fitting plate for the focuser to take the 50mm thread on the gold tube instead of the 2" PST thread the new focuser came with and swapped the eyepiece holder from the PST with one from a standard Skywatcher 1.25" diagonal.

James

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JamesF

JamesF

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I did a quick search and could only find this thread http://solarchat.solarastronomy.org/index.php/en/this-is-solar-chat/6-this-is-solarchat-/71693-hi-there#71693

Doesn't seem to be many using the QHY5 for solar but it looks like the II seems to work better than the older version although this was a colour one.

Alexandra

Oh, the joy of QHY's camera naming schemes.  I assume that as there is no QHY5-II colour camera to the best of my knowledge and because the poster says it was a mosaic that this was actually the colour version of the QHY5L-II.

James

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Stu_2011

Stu_2011

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Short of turning replacement parts up rather than cutting down existing ones, or biting the bullet and doing modding the PST (which can actually be done non-destructively) I think that's a fair summary of your options.

I took the path of modding mine, replacing the focuser unit and shortening the optical path at the same time:

Posted Image

but all that is involved from the PST side is removal of the tube and the eyepiece holder from the "black box" (obviously it does now require a separate finder). I turned up a new fitting plate for the focuser to take the 50mm thread on the gold tube instead of the 2" PST thread the new focuser came with and swapped the eyepiece holder from the PST with one from a standard Skywatcher 1.25" diagonal.

James

Thanks James

That mod looks interesting. I have a lathe / mill so making the bits would be fairly easy. I also have a spare SCT Crayford focuser as well.

I might PM you for some more details at some point if you don't mind?

Stuart

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