First light with the DS PST

[thenews24]

Finally received the double stack unit and had a chance to image a little bit today. And to be honest, am somewhat disappointed. Double stacking the PST seems to be more frustrating than rewarding. Yes, there is a significant improvement in contrast, but all it seems to do is make the filaments more bold, and some slight increase in detail. Which is nice. But now working with 2 etalons, the sweet spot has turned into an evil little demon, making a simple mosaic difficult to blend.

I have 2 images here, both processed the same way, and of the same region of the disc, just taken at different times with different features. The single stack image seems to keep the edges more crisp and prominences much clearer. The double stacked image does indeed bring out more detail on the disc, but the edges are blurred, and the bottom of the disc has what looks to be like a lot of noise and distortion.

Single Stack PST

Double Stack PST

I personally like the single stack image much better. The double stack's increase in contrast is nice, but seems to sacrifice a lot of other qualities.

[DrRobin]

Hi,

Nice comparison. Like you I think you can see more detail in the single stack over a much bigger area. I suspect that using the DS is like getting the single stack right, except it is not twice as difficult, but 2^2 or 4 times the difficulty to get everything right.

I am sure someone who has used a PST with DS will be able to give you a few pointers?

[Merlin66]

Tune for maximum contrast.

The DS narrow band (around 0.5A) definately shows the surface and filaments much better and allows you to see objects in the red and blue wings of Ha (Doppler shifting).

For proms a single stack, having a wider bandwidth is prefered.

Practise, practise, practise

Onwards and upwards.

[thenews24]

I dont know what I'm doing wrong, but have two more comparisons. I tuned for maximum detail, but the single stack still looks way better. I'm no longer fristrated with the actual tuning of the double stack, I'm frustrated by it's price and what it delivers. No way in the world is the 40 mm rich view tumer double stack worth what it cost.

Single stack

Double Stack

[Merlin66]

Hmmmm

You should be getting better results than that.

I assume you're using your DMK41 (with/ without barlow?)

See see some residual Newton's rings in the DS image and the focus looks a bit soft....

What settings are you using on the camera?

What do you use for stacking?

[thenews24]

2.5x Televue powermate,dmk41, I can't quite remember the exp and gain used, but had to bump them both up when using the DS. Using AS!2. I made sure of the focus though. But for some reason the single stack image comes out much clearer, even though it was only stacked and aligned, the same way the double stack was.

Here's another comparison, both roughly same frames, aligned and stacked in AS!2 the same way. No post processing.

Sinlge Stack

Double Stack

The DS seems to really exasperated the Newtonian rings. The filament is bolder with more contrast, but something just feels off.

[Merlin66]

Certainly something wrong there...

The focus still seems to be soft in the DS.

Try a comparison without the powermate. Also you could run the results through Registax see if it makes a difference...

I think maybe the Newton rings are becoming more noticable due to the longer exposure????

(based on other's feedback - the Newton's rings seem to be more defined when you go to extreme narrowband (ie 0.5A v's 0.7A))

[thenews24]

I'll take some more tomorrow and and record specific parameters. I appreciate your help.

[KE400]

I agree with Merlin66, try running through Registax. I can only comment on my own image processing results so far but I wasn't happy with the results of AS!2 compared to Registax 6.

It's probably down to me not utilising AS!2 in the correct way, (apologies Emil), but I've found that when I followed the processing guide regarding solar image processing that was posted by a fellow member on here, (can't remember when and who posted it at the min!!). I found that AS!2 seemed to concentrate on only a selection of the solar image and placed in many alignment points (hundreds) with regard to only that part of the image. This didn't give even results within the image when finally processed.

As a comparison I decided to run through Reg 6 which I understand a little bit more about and then processed the same image, it resulted in a more even and detailed result around the full image too. I'd certainly give it a try and see if the results differ.

I've no experience with your scope set up therefore can't give any other info than try a different process.

Hope this helps

[thenews24]

The processing sn't my issue. The proof is in my raw avi's. Even in the raw video, the single stack looks much better than the double. I just posted the processed images here, since I cant post avi's. But the images I did post, do resemble the raw avi's pretty fairly. My issue right now is the DS and finding out the rights tuning and exp, etc.

[Merlin66]

I'd still try Registax as an alternative. It could be that the stacking program is preferentially picking up on the Newton rings and stacking to suit them rather than the image detail?

If the avi is showing a poor image then double check the optics and focus....

[Merlin66]

Just a thought...

Have you tried the DS etalon at various different radial positions?

Mark the hinge position with a small piece of tape , then unscrew the etalon assembly say 1/4 turn (you could temporarily "lock" the etalon position with a strip of gaffa tape.) Retune to get best contrast...It would be interesting to see if there's any difference/ improvement.

[thenews24]

Yeah, I have tried the DS etalon in multiple positions. I'll post a video later of my operations. But those newton rings are just as strong in the raw avi even before I process it. I'll try adjusting exposure down and see if that helps.

[thenews24]

To show what my avi's look like, threw these up on youtube real quick.

http://www.youtube.com/watch?v=h8loJOinPXQ&feature=youtu.be

Think it is the higher exposure bringing out the rings more in the DS. If its sunny today, will post another video of me adjusting the etalon and all my settings.

[thenews24]

Ok, so filmed without the powermate, and no more rings. Although I did try the powermate with lower exp, and it slightly helped too.

But I went ahead and recorded my entire tuning process. Please let me know what you think.

http://www.youtube.com/watch?v=etUrxFwRUFA&feature=youtu.be

Thanks

[Merlin66]

Great presentation!

Certainly shows what you do.....

A couple of things

You don't mention refocusing when trying to get best image..

The seeing looks average,

If you set and then re-tune both etalons you may be well off band and due to the Doppler shift some parts of some filaments may well dissappear.

I normally set the PST etalon first to give a good contrast, tight image.

Then set and adjust the front etalon ONLY. Don't touch the PST etalon.

Watch for moments of better seeing and run the focus in and out to get a crisp image in the sweet spot area.

I spend probably more time trying to get "best focus" than I do with the tuning...

Camera settings?

Keep the gain down below 300 and adjust the exposure. Don't worry about frame rates, that will look after itself.

[thenews24]

Yeah, couldn't tell you the exact exp and gain I was working with, just adjusted the sliders along the way. I'll take note of under 300 gain though.

Have a lot of figuring out, working with two etalons, but appreciate your advice and responses.

The biggest problem I'm having a the moment is making mosaics with the DS using the 2.5x powermate.

I can adjust the DS etalon to get maximum detail in one particualr area of the disc and everything looks great (besides some rings), but once I move the scope to capture a different section of the dosc, everything changes, not sure if I should just leave it alone allowing generous overlap and trust CS5 photomerge, or re-adjust the eatalon for every different frame window of the disc I'm looking at.

[Merlin66]

i'd like to see far better results with the DS before considering a mosaic.

Mosaics can be challenging! You need to consider making some flats to correct the sweet spot gradients.

[thenews24]

Ok, this will be the last comparison I'll do in this thread, just wanted to share.

Spent a lot more time concentrating on focus today with the DS.

I am happy with improvement in contrast and detail, but no matter how much I tried to maximize focus, the DS mounted seems to blur the image just slightly.

I think my stock PST is just a really good one on its own, but for a last comparison here some images. Both processed same way, the DS lools better besides focus, but I really couldn't get a better focus than that.

Single Stack

Double Stack

Defiantly like the detail and 'softness' the DS brings to PST imaging, but focusing it as well as the single is eluding me.

[Merlin66]

Certainly seems to be an improvement there!

I think you're getting there, the seeing conditions will always be an issue. Maximise the length of the avi and set the quality limit to pick up only the "best" 10-15%

Onwards and upwards