Back to forums

Flats in remote imaging

Equipment Calibration Remote Astrophotography
13 replies•470 views
Arun H avatar
Arun H avatar
Hello -

I am exploring what it would take to set up an extra scope/mount I have for remote imaging, and specifically looking at flat generation. I'd like my flat frames for all filters to be 4s or longer. I have the following questions:
  • How many of you that do remote imaging take sky flats and how well does that work for you? When I have done this, I know the sky brightness changes quite quickly, so timing is critical and I have wondered if there is sufficient time to take an entire series of flats (eg. multiple filters) before it gets too dark.
  • If using a LED panel ike the Deep Sky Dad OFP series - is there sufficient adjustability across the brightness range to achieve a 4s or larger exposure time for all filters without the use of neutral density filters or the like?


Arun
Helpful Insightful Respectful Engaging
andrea tasselli avatar
andrea tasselli avatar
I can't answer the question per se as I don't take this long flat frames. My question is really why should you? Why 4s or more? I think my longest is 3.15s and I could easily fit the whole lot of them in that requirement but I can't for the life of me find a reason for it, so I don't.
Arun H avatar
Arun H avatar
Hi Andrea - that's just my current practice with the 294MM which I'd plan to use due to the whole issue with the timing accuracy.
Dave Erickson avatar
Dave Erickson avatar
Here is a link to a PDF of the control system and considerations for remote imaging using a CDK17 "Off the Grid"

CDK17 Remote Control System-Solar.pdf

 Check pages (54-60) yes the EL panel illumination is romote controllable...
Tony Gondola avatar
Tony Gondola avatar
Two choices really, use a remote controlled flat panel or take sky flats. If you use NINA you can take your sky flats as part of a sequence. You can also control the flat device of you go that route as well. If you need to take super log flat exposures then the flat panel makes sense. That said, the simplicity and dependability of sky flats is hard to beat.
Jeff Ridder avatar
Jeff Ridder avatar
I do sky flats in NINA for my remote scope. Cheap, easy, reliable.

I can typically do up to 4 filters, 20 flats each in a single run.
Mark Savan avatar
Mark Savan avatar
For my remote observatory I use sky flats taken through NINA - either via the Flats Wizard or through Advanced Sequencer. I can get 20 flats for each of my 7 filters in a single sunrise session. I go as short at 1 second for my exposures though
Helpful
Arun H avatar
Arun H avatar
Thank you , all. I am inclined to try sky flats and see how it goes. If anyone has direct experience with the dim ability of the DSD flats, please let me know.
John Hayes avatar
John Hayes avatar
Arun,
I am personally not a fan of sky flats so here's what I did on my ASA600.   It is slightly less elegant that what Dave Erickson did but everything is slightly less elegant that what Dave does--always!! 

Lift Stand Controller 12-26-23.pdf

These are relatively easy to build and mine has worked flawlessly.  If you want to take this on, send me a PM and I can fill in a few "non-public" missing details.

John
Helpful Supportive
Stelios_Stergiou avatar
Stelios_Stergiou avatar
Arun H:
Hello -

I am exploring what it would take to set up an extra scope/mount I have for remote imaging, and specifically looking at flat generation. I'd like my flat frames for all filters to be 4s or longer. I have the following questions:
  • How many of you that do remote imaging take sky flats and how well does that work for you? When I have done this, I know the sky brightness changes quite quickly, so timing is critical and I have wondered if there is sufficient time to take an entire series of flats (eg. multiple filters) before it gets too dark.
  • If using a LED panel ike the Deep Sky Dad OFP series - is there sufficient adjustability across the brightness range to achieve a 4s or larger exposure time for all filters without the use of neutral density filters or the like?


Arun

I’m using a deepskydad flat panel cover 2, almost a year without single issue. I’m sure you get the exposure times you want
Jeff Reitzel avatar
Jeff Reitzel avatar
Hi Arun,
 I don't use sky flats so I can't speak to the first part of your question. I do use both a Deep Sky Dad OFP2 panel and an older Alnitak Flip Flat panel. Like you, I prefer longer flat exposures. I typically use 6s for LGB and Oiii,  and 15s for R, SII, and Ha. It just works well for my rigs and filters and I can't even remember the reason I started doing it. I believe it was something to do with inconsistent readings in short exposures with CMOS sensors when they were first introduced to our hobby. Perhaps it is baseless now? Anyway,  there is no issue at all with having a range of brightness settings that work at these exposure lengths with either flat panel. Both are easily controlled with ASCOM drivers and the programs I use to automate flats any time I need to take them. I mainly use Voyager but have also done this in NINA without issue. 

CS,
Jeff
Well Written Helpful Respectful Concise Supportive
Arun H avatar
Arun H avatar
Thanks again for the responses.

I should have mentioned what I will be using. It is really a small setup - an AP Mach 2 mount with a 92mm Stowaway (I have a Mach 1 which I plan to use at home with my other scopes, the Mach 2  is just better suited to remote operation). Anyway, space at the site is a constraint, hence a panel which can be attached to the scope, or sky flats. I don't have a desire (yet!) to image with large scopes, my main goal is to get away from the frustration of smoke and clouds and light pollution.

@Jeff Reitzel ​​​​@Stelios_Stergiou  - thank you for the vote of confidence on the DSD, that's probably what I'll purchase based on your recommendations. I saw that it can be controlled digitally from a level of 1 to 4096, but wasn't sure if these actually translated to meaningful changes in brightness.
Respectful Supportive
Willem Jan Drijfhout avatar
Willem Jan Drijfhout avatar
Yes, @Arun H , the controller settings from 1-4096 are definitely meaningful. I use DSD panels all the time (30cm and 60cm). These are not mounted on the scope. But as far as I understand, the controller of all DSD panels is the same. And it is the best controller I have seen so far, and have tested many.
First of all you get the large range like you point out (1-4096)
But even more important, the range is linear across all settings. So 2048 will give you half the brightness of 4096. And 8 will give you half the brightness of 16, etc. 
Also the maximum brightness of it being a LED panel is sufficient for narrowband filters as well.

As for your application: 
On the brightest side, I can get 30,000 ADU in 10s exposure on an 106mm/f5 scope for luminance @ gain 100 using panel setting 8. 
On the dimmest side, for my 3nm narrowband SII on the same scope, I need 6s @ setting 4000 for and ADU of 30,000.
So in this case you could choose 6s as your 'one and only' exposure time and work your way across all filters. 
Obviously scope, camera, NB bandwidth etc. will have an effect on your final outcome, but the panel will give you lots of flexibility.
Helpful Engaging
Arun H avatar
Arun H avatar
Willem Jan Drijfhout:
Yes, @Arun H , the controller settings from 1-4096 are definitely meaningful. I use DSD panels all the time (30cm and 60cm). These are not mounted on the scope. But as far as I understand, the controller of all DSD panels is the same. And it is the best controller I have seen so far, and have tested many.
First of all you get the large range like you point out (1-4096)
But even more important, the range is linear across all settings. So 2048 will give you half the brightness of 4096. And 8 will give you half the brightness of 16, etc. 
Also the maximum brightness of it being a LED panel is sufficient for narrowband filters as well.

As for your application: 
On the brightest side, I can get 30,000 ADU in 10s exposure on an 106mm/f5 scope for luminance @ gain 100 using panel setting 8. 
On the dimmest side, for my 3nm narrowband SII on the same scope, I need 6s @ setting 4000 for and ADU of 30,000.
So in this case you could choose 6s as your 'one and only' exposure time and work your way across all filters. 
Obviously scope, camera, NB bandwidth etc. will have an effect on your final outcome, but the panel will give you lots of flexibility.

This is perfect. My scope is f/5.3. Thanks for the detail! This seems like a really nice panel set. My current EL panel has virtually no brightness controllability, so I am left with using sheets of paper to modulate the output. Which is fine for backyard imaging but not for remote.
Well Written