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Looking for an SCT Target

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11 replies to this topic

#1 RatBiscuit225

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Posted 14 February 2020 - 02:26 PM

I've spent the better part of 5 years imaging at prime focus with a fast Newtonian, but tonight I'm taking my new 8" SCT out for first light!  Since I have no experience with deepsky imaging with such a setup, I'm looking for target recommendations for a SCT newbie, along with any general advice that I might not have thought of working with a Newtonian for so long.  Anything you can contribute to make my first clear night with the new scope will be much appreciated!  I know it's a little early in the year for galaxies, but I want to get my silly mistakes out of the way now so that when spring hits in full force I'm prepared for the pitfalls that surely await me.



#2 bignerdguy

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Posted 14 February 2020 - 03:01 PM

First thing i will suggest is if this is not an Advanced ComaFree scope you will need to get a field flattener/focal reducer for it.  SCT's have a lot of field curvature so trying to photograph with out one will leave you less than impressed.  Plus even a small SCT has a long focal length so is rather high powered without one as well.  However with even an 6" SCT you can image things like galaxies, nebula, and with a barlow even planets.  A good place to start that is an easy target is the orion nebula.  Its bright, easy to find and works well even visually.  Its where i started...



#3 BobE102330

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Posted 14 February 2020 - 03:05 PM

I use https://tonightssky.com/MainPage.php to help decide what to shoot.  Then head into Stellarium and/or NINA to check framing.  M81 fits a bit tightly in your FOV, which should make it easy to spot. 

 

What are you using for goto and acquisition software? 

 

I'm a 9 month newbie but found NINA intuitive and works well with a rig similar to yours.  Using ASTAP plate solving in NINA makes finding the targets a lot easier than using the Orion mount's goto after a three star alignment.  I'm hoping to get pulse guiding going tonight.  My first try failed, I think because the ASCOM driver defaulted to minimum guide speed.  ST-4 guiding worked reasonably, but I'm hoping for better from pulse guiding.

 

Given the importance of accurate guiding at long focal lengths, I would treat the first light as mostly a guiding tweaking session.  Sure, you'll take images to judge if the guiding is working well enough and tweak settings as required.  

 

Good luck with your new scope.



#4 JohnKulczycki

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Posted 14 February 2020 - 03:07 PM

Double cluster.

Be prepared for longer exposures because you are now at F10

See:
https://pmo.uoregon..../open-clusters/


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#5 rk2k2

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Posted 14 February 2020 - 03:46 PM

I'll assume you aren't using a reducer hence your C8 is roughly 2000mm/ f10 and you'll be using an APS-C sensor.  I'll also assume your Atlas has fairly close GOTO's   M81 and M82 would be great targets.  Since this is first light, I recommend setting up your imaging train on a daytime target to where you have things 'ballpark' and able to focus with enough inward focus left for infinity at night.  I didn't and I found myself struggling in the dark to get the right spacing and focus.  At f10, a 2 minute exposure at iso1600 should get you something though 3 minute to 5 minute will be better. Of course that depends on your seeing. 



#6 RatBiscuit225

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Posted 14 February 2020 - 04:00 PM

What are you using for goto and acquisition software? 

 

I've been using "old" PHD (i.e. not PHD2) for guiding and never had any trouble with it.  For actual image capture I've just got an interval meter hooked to my camera and do all my capture without computer interface.  May be worth learning my way around some new software though as critical as guiding seems for an f/10 scope.  Is NINA designed just for guiding?

 

A good place to start that is an easy target is the orion nebula.  Its bright, easy to find and works well even visually.

 

I'm surprised that will fit into my FOV, I figured it was too large a target to capture.  This seems like it might be a good first option, it was my first-ever successful image with my Newtonian.



#7 RatBiscuit225

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Posted 14 February 2020 - 04:04 PM

I found myself struggling in the dark to get the right spacing and focus

This may be a stupid question - but what exactly do you mean by "spacing"?  I've heard this mentioned before, but I've always just focused in the field by getting my rig set up, then shooting a couple test exposures on a bright star near my target.  I'm self-taught in this hobby so there are a lot of terms I'm not familiar with, unfortunately.


Edited by RatBiscuit225, 14 February 2020 - 04:07 PM.


#8 rk2k2

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Posted 14 February 2020 - 05:13 PM

This may be a stupid question - but what exactly do you mean by "spacing"?  I've heard this mentioned before, but I've always just focused in the field by getting my rig set up, then shooting a couple test exposures on a bright star near my target.  I'm self-taught in this hobby so there are a lot of terms I'm not familiar with, unfortunately.

If you get focus you needn't worry about it.  I'm not talking about image sensor spacing from a field flattener that is often talked about, I'm talking about the entire spacing from the sensor to the draw tube.  What I mean is you have a T-adapter on your camera which eventually attaches to the draw tube.  For my scope (VC200l) I had to add about an additional 1-2" in extension tube between the T-adapter and the nose piece attaching to the draw tube.  You may or may not need an extension, better to find out during the day than at night when you're trying to image (like I tried to do).



#9 bobzeq25

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Posted 14 February 2020 - 05:20 PM

I've been using "old" PHD (i.e. not PHD2) for guiding and never had any trouble with it.  For actual image capture I've just got an interval meter hooked to my camera and do all my capture without computer interface.  May be worth learning my way around some new software though as critical as guiding seems for an f/10 scope.  Is NINA designed just for guiding?

 

 

I'm surprised that will fit into my FOV, I figured it was too large a target to capture.  This seems like it might be a good first option, it was my first-ever successful image with my Newtonian.

Guiding is going to be _much_ harder at the longer focal length.  Most people use an off axis guider.  Google <mirror shift SCT>.

 

NINA is a swiss army knife for data capture, it handles many functions.  You need to do some research about it.

 

I like the double cluster idea, that will define the issues best.  There will be issues.  <smile>

 

But you could shoot M42, the fact that you won't get it all does not matter.  For some time, this is going to be about getting things working, not winning Image of the Day.  <smile>

 

The F6.3 reducer would make things a lot easier.


Edited by bobzeq25, 14 February 2020 - 05:22 PM.


#10 Stelios

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Posted 14 February 2020 - 05:35 PM

Use Telescopius to search for targets. Enter your location, then start with Galaxies and Bright Nebulae (also Planetary Nebulae if so inclined), and put in apparent size of 5 to 30 arcmin. Specify that they stay above 35 degrees for at least 3 hours. 

 

Some gorgeous targets are out there. It's actually the best time to image with an SCT. But--as already mentioned--you will NEED the F/6.3 reducer/flattener. 

 

M81 you can shoot all night long. The Crab Nebula (M1) is a great target for early evening. 

 

Of course if you like globs and clusters you can also select these in addition to galaxies and Bright Nebulae. 


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#11 bignerdguy

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Posted 15 February 2020 - 07:32 PM

 

But you could shoot M42, the fact that you won't get it all does not matter.  For some time, this is going to be about getting things working, not winning Image of the Day.  <smile>

 

The F6.3 reducer would make things a lot easier.

Definitely.  M42 will mostly fit in the image but as said it isnt about hubble quality images, its about learning the craft.  Plus you would be surprised how beautiful even a closeup shot of some objects can become in the final output.  M42 is no exception.  Lots of colors and dust lanes make a close up shot of the core worth trying for on a first time image.



#12 RatBiscuit225

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Posted Yesterday, 03:24 PM

Thanks for all of the advice.  Last night and the night before I was able to test out a lot of the setup and guiding process.  Seems like it's more in-depth than setup with my Newtonian, but definitely a challenge I'm up for.  One weird issue I had - for my 25mm eyepiece with my diagonal, I got an oval-shaped FOV.  This doesn't happen without the diagonal, nor does it happen with a different eyeypiece.  I can use the 25mm and the diagonal together on my refractor and have never had this problem.  Do you know what would cause this?




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