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Ant

PST and DFK focusing

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Hi all,

I've been lucky enough to be loaned a PST and DFK for the transit.

I was really hoping that there were going to be some sunny spells between now and then so that I could practise.

But looking at the weather it's looking a little unlikely, so I have a few question?

I have never used a PST before or imaged the sun with anything other than white light filter and a digicamera. So please make this simple.

1. Will I be able to get focus ok with just the PST and DFK?

2. I will be using a static tripod, so what will the image scale be like?

3. How long will the sun be in the FOV? I also have been lent a 2.5 TV power mate. If I add that same question.

4. Do you do the same as the moon/planets and take a 1000 frame avi and stack it? Or smaller ones? Or single frames?

5. Which codec should I use, as I'm not going to get a second chance at this.

6. Can anyone give me a ball park on the exposure times needed? Just so I can start in roughly the right place.

Sorry for lots of questions, but I'd really appreciate some guidance.

Cheers

Ant

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Which DFK camera? the 41 will give you a full disk, the 21 and 31 will clip the disk.

The PST is a 400mm FL scope and you should use Y800, the default. Take a video around 1000frames or more and then use registax to create a single image.

With the gain at 100 on a DMK41 typical exposures will be 1/100 - 1/15 second depending on whether you want the surface detail or prominences.

The sun subtends an angle of about 0.5 degrees and moves at 15 degrees an hour

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Is there no way you can get it on a driven mount Ant? Trying to focus when the sun moves so quickly is a recipe for frustration I found! The DMK probably won't come to focus without a barlow unless you have a low profile nosepiece.

Helen

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Camera also needs a shoulderless 1.25" nosepiece to get to focus.

DFK isn't ideal for PST, a DMK would be much more suitable, but if it is what you have, it's what you have :hello2:

Cheers

Ian

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I have a dmk21 myself, but Jon suggested that maybe colour would be better for the transit. But if the general opinion is b&w is better then I'll go with that.

Helen, I do have a little eq1 but to be honest I have the single speed motor but I'm not a fan. But I could give it a go...

A clear day to get everything focused would be very useful, I could then just leave everything attached in the right position.

I thought y800 was a b&w format?

Boy am I out of touch... :)

Thanks for the tips Kevin. 1000 frames it is, I wasn't certain what with the suns boiling surface that I've seen in movies...

As you can tell I really have no idea :hello2:

Ant

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DMK21 mono at 60fps will give you the best detail and help overcome any turbulence with the sun so low on the horizon. It will be much better than a colour chip IF you can handle the magnification.

This simulation is with a 21 and 41 on an 1100mm refractor taken over an hour so you can see what your 21 on a PST will give you (very similar to my DMK41 on the 1100mm)

[media=]

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I've just seen your reply Ant. I'd go mono unless the colour cam has a 41 chip. Mono is more sensitive and will be much easier to process,and as all you're capturing is part of the red spectrum (that's all the Ha filter lets through) then adding colour in post processing is easy.

Helen

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Ant,

Yes, Y800 if using a mono camera. Also would go with the DMK21 if you can handle the speed the sun will move out of shot. PST is monochromatic, so although colour will work, mono will work better. Also easier to get a good exposure too.

Remember, at dawn, the sun will travel at a non linear speed due to atmospheric refraction, so a tracking mount won't help much immediately after it breaks the horizon.

Also bear in mind that the luminosity will also change quickly at dawn. So the faster you can get your 1000 or so frames in the bag, the better. You'll have to keep checking the exposure before each capture.

As for testing, you may get some clear spells up your way on Monday if you'll get the chance.

Cheers

Ian

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If you have access to a EQ3 or better then you could use the DSSR software to use the TIS camera video to track on Venus or some sun surface detail that will handle any non-linearity in speed.

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Indeed. I really like the look of the DSSR software (new release the other day) as I'd like to do day long time lapse of proms. Just waiting on a EQDIR box for the mount.

Cheers

Ian

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Indeed. I really like the look of the DSSR software (new release the other day) as I'd like to do day long time lapse of proms. Just waiting on a EQDIR box for the mount.

Cheers

Ian

At the moment, EQDir isn't the best way to connect the mount for DSSR control as EQMod doesn't allow 3rd party software full access to the motor parameters for pulse guiding.

Connecting the mount via the handset to a computer is the better option until Dave can resolve the EQMod method.

Edited by Photosbykev

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Thanks for all the tips:)

Managed to get out today and see what's what. Glad I didn't rush out into the field for the transit without preparation... I would have failed

Kevin's spot on - the DMV does not focus in the pst. Because I'm going to be using a static tripod I didn't fancy the magnification of the 2.5 Barlow... I had a rummage and found a 2xbarlow that had an unscrew able element. So that is now screwed into the front of the DMK. This roughly should give about a 1.4 increase and let me focus :).

Helen your right a driven mount does make life easier, so I've used the heq5 to help me practise and get the PST/DMK focused. I have now removed everything in one piece ready for the morning. The location i'm going is about 3/4 of a mile from home - I do not have an extension lead long enough :D

Ian, yep clear today for a bit, so I've been out practising.

Cheers all Ant

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Thanks for all the tips:)

Managed to get out today and see what's what. Glad I didn't rush out into the field for the transit without preparation... I would have failed

Kevin's spot on - the DMV does not focus in the pst. Because I'm going to be using a static tripod I didn't fancy the magnification of the 2.5 Barlow... I had a rummage and found a 2xbarlow that had an unscrew able element. So that is now screwed into the front of the DMK. This roughly should give about a 1.4 increase and let me focus :).

Helen your right a driven mount does make life easier, so I've used the heq5 to help me practise and get the PST/DMK focused. I have now removed everything in one piece ready for the morning. The location i'm going is about 3/4 of a mile from home - I do not have an extension lead long enough :D

Ian, yep clear today for a bit, so I've been out practising.

Cheers all Ant

The DMK cameras do focus on the PST BUT you need to use a short nosepiece without a shoulder so that the front of the camera casing touches the top of the eyepiece tube and make sure you remove the C/CS adaptor ring from the front of the camera body

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Ok I re-phrase it :D Out of the box the DMK doesn't focus with the PST. I don't have the time to get a low profile adapter. Or the tools (or permission) to adapt Jons :)

I happy enough that I got it to focus with the barlow and managed to get an image. Hopefully it'll be clear for a little while before I have to give it all back!

Cheers

Ant

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Ok I re-phrase it :D Out of the box the DMK doesn't focus with the PST. I don't have the time to get a low profile adapter. Or the tools (or permission) to adapt Jons :)

I happy enough that I got it to focus with the barlow and managed to get an image. Hopefully it'll be clear for a little while before I have to give it all back!

Cheers

Ant

as long as it works and the weather plays ball I think there are a lot of people that will be happy :)

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The weather (forecast) has changed so many times of the course of today, we now have sunny intervals forecast. 6 hours ago all that we had for tomorrow was rain all day.

Here's hoping.

Ant

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