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Lots of questions- UV/IR Cutoff, ASI OAG, Guiding(PhD), NINA, Mosaics, Field Flattener

Astrophotography Beginner DSLR DSO Equipment Reflector Software
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#1 Astrolamb

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Posted 16 June 2021 - 11:01 AM

Any and all advice and knowledge is more than welcome and in advance I'd like to say that I appreciate the help very much. 

 

Yes this is a long post, but I'll separate the questions into categories to make it easier for anyone to respond to what they know about. Before the questions here is a little background of where I am at. 

 

After doing the full-spectrum mod on my camera I'm happy and I liked the results, but realized how limited my exposures were in terms of capturing the dynamic range of the targets I was imaging. Without guiding I am limited to around a 1600ISO 60s exposure at my local dark site and that keeps my average ADU at about 850. At home in the backyard I am limited to 200ISO 60s because of light pollution. I also noticed that even though I had kept the average ADU at the bare minimum I was still blowing out most of the brighter stars in my frames.

So during all of my cloudy weather I decided to make the push for guiding and while I was at it I ended up purchasing a ZWO UV/IR cutoff filter to get me by during the time being. 

After nearly 2 months of cloudy weather, its about to be summertime in Texas. For me that means, many clear nights with relatively good seeing are ahead!

Tonight is actually one of the first nights where it will be dry enough on the ground that I feel confident about setting up my equipment so I will be testing the new hardware for the first time and trying to learn the software tonight! Since tonight is the first night I would like to hit the ground running and know what pitfalls to avoid and what to expect, so on to the questions!

 

Current Equipment:

8" 1188mm FL Reflector

Celestron ASGT Mount (hyper-tuned, balanced, and recently re-meshed)

Moonlite Dual Speed Focuser

Full-Spectrum Modified Nikon D5300

 

Current Software:

Backyard Nikon

Astrotortilla

Iris(To check ADU)

 

New equipment: 

-ASI 290MM Mini

-ASI OAG

-ASI Helical Focuser

-ZWO UV/IR Cutoff Filter

 

Future purchase:

Field Flattener

 

Questions:

 

ZWO UV/IR Cutoff Filter:

To anyone that has or has had this filter, does it work good enough to start out with? 

Is there anything I should know in advance about spacing between the filter and the camera?

I plan to use it in this configuration: Camera->T2 Ring->OAG->Moonlite M42 Adapter->UV/IR Cutoff->Telescope; Does this look okay?

 

ASI OAG and Helical Focuser:

*I went with the Helical Focuser as well to make it a bit easier on myself, I know many people say I don't need it but I wanted to ensure I wouldn't be adding another possible issue into everything.*

I have read some people recommending that I test the depth of the prism by taking flat frames first, is this a good way to do it? 

Since I don't have a field flattener yet, will having the prism that close to the edge will it effect PhD's ability to guide or find stars? 

Are there any other quirks about the OAG and helical focuser I should expect?

 

ASI 290MM Mini:

For this camera, should I use a dark library or should I use a bias library in PhD?

How much does it matter what temperature I take the library at? 

Are there any weird quirks I should know to expect about this camera beforehand?

 

PhD:

I have read through the manual and often recommended literature about PhD, but I would like to know any personal recommendations on settings I should use or avoid.

I have seen people discuss multi-star guiding with a different software, is this possible or necessary with PhD?

Since my imaging camera is sampling at ~.6 arcsec/pixel, what guiding numbers should I be aiming for to take a "infinite" exposure?  

 

NINA:

I would like to use NINA to help with automatic meridian flips as well as keeping better track of my acquisition throughout the night, is it possible to use NINA with a Nikon D5300? I couldn't find any literature that would confirm or deny the compatibility.

Coming from Backyard Nikon NINA seems fairly complex, it has a great layout that helps make it seem intuitive, but what settings do I actually use to just start a sequence? Can I just start a sequence from the sequence tab or do I need to have an entire plan saved for my night? 

How do you plan mosaics in NINA? 

Are there any good guides I can browse through to learn about all the ins and outs that NINA has?

*I have not read any NINA literature yet other than some peoples reviews of it on here, I have looked to see if it had a help wizard but I could not find it.* 

 

Mosaics:

I would like to start taking some mosaics, specifically for targets that are larger than what my camera's FOV will capture. Can I do this without a field flattener? 

Will I need to overlap my frames further to keep stars from having oblong shapes? 

I know this is almost a SNR question, but lets pretend for a moment that I have perfect skies, how many frames should ideally be stacked to help eliminate the overlap lines and keep stars a uniform shape? 

 

Drizzle and Dither:

*I know that a true drizzle will not work unless the image is being dithered, I also know that it takes about 20 subs to make a "true" drizzle begin to work properly.*

Since my mirror is 8" and the theoretical seeing limit of it is ~.6 arcsec/pixel, will proper use of drizzling help me get closer to the theoretical limit?

With proper use of drizzling can I pass this theoretical limit of the mirror?

How many pixels should I be dithering if I wish to drizzle for increased sampling?

Should the amount that I dither each sub change if I use 3x drizzle vs 2x drizzle?

Is there a difference in the accuracy of a 2x vs a 3x drizzle? 

Is there a visible difference in the quality of that accuracy difference?

 

Field Flattener:

My next purchase will definitely be a Field Flattener, but most of the flatteners I have found are marketed towards SCTs.

Can anyone recommend a quality flattener for use with a Newtonian reflector?  

Since my FOV is already less than a degree I would prefer a flattener that acts as a reducer instead of a barlow, but is that even possible? 

The secondary mirror on my scope is smaller than the stock mirror it came with, so I don't believe I will actually be able to use a true reducer on it. I do think I could get away with cropping the outer edges of a .9 reduction though if it was necessary. 

 

Thank you again to everyone who took the time to read all of my questions and/or reply! I am sure more questions will develop but I think I have covered all of the big points that have been rattling around in my head lately.. 

 

If anyone has any recommendations of specific data I should collect tonight to post here that will help tune my new equipment please let me know! 



#2 John Tucker

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Posted 16 June 2021 - 11:21 AM

I can't comment on a lot of these questions.  The one thing I would point out is that you make sure you pick out a coma corrector (this seems to be what they call the Newt corrector analogous to an SCT field flattener for some reason) that has enough backfocus distance for your DSLR and OAG.   Its real common for Newt coma correctors to have backfocus distances of 62mm or less.  Your camera body will use 44mm of that and a standard Canon T adapter will use another 10 or 11mm.  (short path adapaters of 2 to 3 mm are available, for example from Baader and TS Optics).  GSO makes one with 70mm backfocus but I don't have any experience with it to tell you if it is good. 


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#3 sbharrat

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Posted 16 June 2021 - 11:24 AM

...

 

Questions:

 

...

 

PhD:

I have read through the manual and often recommended literature about PhD, but I would like to know any personal recommendations on settings I should use or avoid.

I have seen people discuss multi-star guiding with a different software, is this possible or necessary with PhD?

Since my imaging camera is sampling at ~.6 arcsec/pixel, what guiding numbers should I be aiming for to take a "infinite" exposure?  

 

NINA:

I would like to use NINA to help with automatic meridian flips as well as keeping better track of my acquisition throughout the night, is it possible to use NINA with a Nikon D5300? I couldn't find any literature that would confirm or deny the compatibility.

Coming from Backyard Nikon NINA seems fairly complex, it has a great layout that helps make it seem intuitive, but what settings do I actually use to just start a sequence? Can I just start a sequence from the sequence tab or do I need to have an entire plan saved for my night? 

How do you plan mosaics in NINA? 

Are there any good guides I can browse through to learn about all the ins and outs that NINA has?

*I have not read any NINA literature yet other than some peoples reviews of it on here, I have looked to see if it had a help wizard but I could not find it.* 

 

...

That's a lot of questions, most of which I have no idea about. Some one-line answers to at least give you a basic idea on your Phd and NINA questions.

 

- multistar guiding is in phd2. You simply have to enable the option for it (it is off by default, at least in the version I have). In general it does no harm though I recall reading some folks with small prism OAGs had problems with it. 

- for recommended settings, make sure you run the Guiding Assistant. Most of the values that are non-default will come from that. 

- I would certainly create a dark library for it... don't want to go chasing a hot pixel

- for me, I target less than my image scale. But for me, that is 1.6"/px which usually do-able. Imagine hitting 0.6 consistently might be much harder. 

 

- NINA has built in Nikon driver support. I have to imagine that this supports D5300 but hopefully someone actually using that can comment.

- if you use the simple sequencer (only one in the GA build), you simply find your target in SkyAtlas (or Framing Assistant) then transfer to a sequence. You can then edit the sequence (to specify exposure time, # exposures, dither, etc) if necessary and kick it off. 

- I know mosaic planning is part of NINA but I personally haven't used it. 

- Search for Cuiv the lazy Geek's YouTube videos. He seems to have one for most functions in NINA. I have found his to be the most helpful for me because of the start-to-finish tutorial nature on the topic.


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#4 Astrolamb

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Posted 16 June 2021 - 11:52 AM

I can't comment on a lot of these questions.  The one thing I would point out is that you make sure you pick out a coma corrector (this seems to be what they call the Newt corrector analogous to an SCT field flattener for some reason) that has enough backfocus distance for your DSLR and OAG.   Its real common for Newt coma correctors to have backfocus distances of 62mm or less.  Your camera body will use 44mm of that and a standard Canon T adapter will use another 10 or 11mm.  (short path adapaters of 2 to 3 mm are available, for example from Baader and TS Optics).  GSO makes one with 70mm backfocus but I don't have any experience with it to tell you if it is good. 

That's awesome, that will help me a ton to find a good coma corrector! I didn't know that was the difference. Also, thanks for the forewarning on backfocus!

 

 

That's a lot of questions, most of which I have no idea about. Some one-line answers to at least give you a basic idea on your Phd and NINA questions.

 

- multistar guiding is in phd2. You simply have to enable the option for it (it is off by default, at least in the version I have). In general it does no harm though I recall reading some folks with small prism OAGs had problems with it. 

- for recommended settings, make sure you run the Guiding Assistant. Most of the values that are non-default will come from that. 

- I would certainly create a dark library for it... don't want to go chasing a hot pixel

- for me, I target less than my image scale. But for me, that is 1.6"/px which usually do-able. Imagine hitting 0.6 consistently might be much harder. 

 

- NINA has built in Nikon driver support. I have to imagine that this supports D5300 but hopefully someone actually using that can comment.

- if you use the simple sequencer (only one in the GA build), you simply find your target in SkyAtlas (or Framing Assistant) then transfer to a sequence. You can then edit the sequence (to specify exposure time, # exposures, dither, etc) if necessary and kick it off. 

- I know mosaic planning is part of NINA but I personally haven't used it. 

- Search for Cuiv the lazy Geek's YouTube videos. He seems to have one for most functions in NINA. I have found his to be the most helpful for me because of the start-to-finish tutorial nature on the topic.

That's what happens when you have 2 months of clouds and new equipment you haven't gotten to use! 

I did run the guiding assistant in the garage to set it all up and get a feel of the program so I have all of the values set from that already, any idea how much it matters about the temperature I took the dark library at? Will about 10 degrees make a big difference? I'm planning on redoing it for major temp changes already but I wasn't sure just how much of an impact it would make for smaller temp changes.

 

That's great to know about the driver support, as I was browsing through NINA I figured that was how I would go about it but I still wasn't sure since it has the SkyAtlas/Framing Assistant.

Perfect! I will look up Cuiv the lazy Geek's NINA tutorial and give it a watch!

 

Thanks a ton! 



#5 sbharrat

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Posted 16 June 2021 - 12:53 PM

That's awesome, that will help me a ton to find a good coma corrector! I didn't know that was the difference. Also, thanks for the forewarning on backfocus!

 

 

That's what happens when you have 2 months of clouds and new equipment you haven't gotten to use! 

I did run the guiding assistant in the garage to set it all up and get a feel of the program so I have all of the values set from that already, any idea how much it matters about the temperature I took the dark library at? Will about 10 degrees make a big difference? I'm planning on redoing it for major temp changes already but I wasn't sure just how much of an impact it would make for smaller temp changes.

 

That's great to know about the driver support, as I was browsing through NINA I figured that was how I would go about it but I still wasn't sure since it has the SkyAtlas/Framing Assistant.

Perfect! I will look up Cuiv the lazy Geek's NINA tutorial and give it a watch!

 

Thanks a ton! 

I created my guide cam dark library in phd2 in January. Have not updated it and certainly more than 10 degrees consistently. Personally, I wouldn't think you need to redo it unless you ran into a case where phd was chasing a (new) hot pixel. 

 

As a beginner, I used SkyAtlas more than Framing Assistant. The former puts the target exactly centered with 0 degree rotation which was fine for me. Then just hit the transfer to sequence button. Go into the sequencer tab and you will see the target there. You just need to set the value for exposure time, number of images, and dither. If you to reuse multiple nights, then ensure that the center and sync settings are on (don't remember exact name) and save. 




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