Another usefull Photoshop Technique to try...

[marktownley]

Intersting the way the thread has developed...

Completely agree with Alexandra - in double stack mode with the SM40 I can easily capture surface and proms in one go; yes, I know the proms aren't as 'bright' as doing a seperate prom shot, but with post processing I can do a pretty decent job of pulling out the prom detail. It's only when the sun is low and seeing is bad that I struggle to do this.

I'm running a USB DMK31 and on 260 gain (minimum) and 100 gamma (default) and with my DS40 @ f21 I operate at 1/37s when the sun is low in the sky, 1/45s when the sun is high. I find with the contrast i'm getting from my DS 100 gamma works for me for one shots...

What f-ratio are you working at Ken? I know the DMK41 is slightly less sensitive than the 31, but 1/11s for proms seems really low to me (compared to what I run at) - especially seeing as you are working at 60mm aperture compared to my 40mm.

[Merlin66]

Seriously, I need separate exposures....
I usually run at around f25 with the double stack.
This was the case when I started with a DMK21 as well...

[marktownley]

Lose an ERF on the inner etalon, I reckon you'll get your prom exposures upto more like 1/27s

[Photosbykev]

with the DMK41 on my LOHA 4" f/11 scope I normally shoot two exposures. The proms are typically 1/15second and the surface detail 1/150sec with gain at 260 and gamma 100.

I have played with the gamma to get a single image containing proms and surface detail but found I had to really push the post processing to get the best out of them which introduced a lot of noise as the proms tended to be under exposed.

[Merlin66]

Kev,
That seems to match my experience.
Mark, at this stage I'm not prepared to dismantle one of the SM60...
I was wondering though...could it be my exposures are so affected by the tuning I apply between the double stack filters? I really do spend a lot of time setting each filter and then working them together to get the "best" narrowband performance.
Typically the intensity, from a single stack, or when both filters are tuned together for Ha is reduced by 50% when they are set for 0.4A bandwidth. This would mean x2 exposure durations for the same settings.....
(Has anyone else measured this?)
Any comments?

[Montana]

Hi Merlin,
I typically have an exposure of around (can't remember exactly) 1/60-70 for SS and when I double stack the PST I go down to 1/25 or 1/19 or thereabouts for surface detail.

Regards
Alexandra

[marktownley]

Mark, at this stage I'm not prepared to dismantle one of the SM60...
I was wondering though...could it be my exposures are so affected by the tuning I apply between the double stack filters? I really do spend a lot of time setting each filter and then working them together to get the "best" narrowband performance.
Typically the intensity, from a single stack, or when both filters are tuned together for Ha is reduced by 50% when they are set for 0.4A bandwidth. This would mean x2 exposure durations for the same settings.....
(Has anyone else measured this?)
Any comments?

Fair play Ken if you don't want to take one apart, however it is only all screwed together so is easily reversible (I will stop going on about it though!).

Regards my tuning the outside etalon (furthest from objective) I never adjust the position of - it is set up so that the reflection is thrown wide of the actual solar image. I've adjusted the hinge plate to do this and the t-max tuner remains locked closed permanently - not adjustment ever since needed. The inner etalon (closest to objective) is a similar setup - again hinge plate adjusted accordingly, t-max tuner locked shut for best position. To adjust for optimum tuning from one observing session to the next I simply rotate the dew shield the etalons are mounted on; this has the slightest sag in it due to weight of etalons and provides just enough variation in tilt required to tune - even in winter in cold temperatures and high atmospheric pressure.

There are a couple of things you can check for Ken if you haven't done so already; are the 2 t-max tuner units diametrically opposite each other? This gives the best contrast... Also have you checked the alignment of the hinge plates? - they offer some adjustment and if not true can affect resultant contrast...

[marktownley]

Hi Merlin,
I typically have an exposure of around (can't remember exactly) 1/60-70 for SS and when I double stack the PST I go down to 1/25 or 1/19 or thereabouts for surface detail.

Regards
Alexandra

What f-ratio is this at Alexandra?

[Montana]

Oh yes, that's when I have the 2x Barlow in as this is when I use the DStack most, sorry!

Regards
Alexandra

[Merlin66]

Mark, et al,
I've gone back to the double stack SM60 thread and added my comments on tuning a DS, rather than this thread.