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StarSense Explorer 102 Refractor: hopeless for EAA?

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#1 Gen166

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Posted 05 February 2023 - 03:19 PM

I’m trying to figure out the right rig for getting into EAA with my 10-year-old.  Reading the various posts here and beginners guides on other Astro websites has taught me lots of things I would buy if budget constraints didn’t exist, but I need to learn what the *next* improvement priority needs to be if we are to have any change at decent images (not hopelessly blurry) of the planets, lunar surface, and maybe some star clusters and nebulae if we feel lucky.

The Problem:

We can’t get sharp captures at all, even though we’re using an ASI 662 camera and SharpCap and running strings of short exposures that add up to about 4 mins of data when combined in DeepSkyStacker.

Current Gear:

StarSense Explorer 102DX with the plate-solver mirror attachment

on the stock Alt-Az mount and tripod that came in the box

ASI 662 camera (brand new)

Laptop (Windows, fast Intel CPU, 16GB RAM and 500GB SSD)

 

Help me prioritize upgrades?

 

A. Image train: I can’t get focus with the 102DX straight into the ASI camera unless I use my Svobony Diagonal.  (I got that because the plastic diagonal that came with the scope was really rough). Should I get a spacer that would allow me to take the diagonal out of the train?

 

B. Scope: We got the 102DX as a family toy a couple years ago.  It’s  F6.7 and FL is 660, so the camera FOV isn’t great (small sensor), but the platesolving bracket works pretty well, and we’re finding stuff fine.  It’s just … impossible to get crisp focus. (Yes, we’ve used a Bahtinov mask) Even when we leave the scope outside so it’s nice and adjusted to the temp.  Even the moon is fuzzy.  There’s also chromatic aberration, but that’s to be expected.  Is the dinky focuser our problem?  Any way to fix?  Or do we just need better glass?

 

C. Mount: Manual Alt-Az mount means we’re constantly chasing stuff across the field of view.  E.g. we tried shooting the Famous Comet and it would only stay in frame for about 30 seconds and then we’d have to move the scope, wait for the vibrations to settle down (about 5 secs) and start again.  I thought startracking wasn’t needed for EAA because you’re just doing short bursts anyway.  But would a Sky-Watcher Star Adventurer GTi change our results more than anything else?

 

Thanks in advance for your collective wisdom…



#2 alphatripleplus

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Posted 05 February 2023 - 03:43 PM

e Problem:

We can’t get sharp captures at all, even though we’re using an ASI 662 camera and SharpCap and running strings of short exposures that add up to about 4 mins of data when combined in DeepSkyStacker.

 

First of all, if you are doing EAA and using SharpCap, why are you not doing live stacking within SharpCap? SharpCap's live stack algorithm should automatically stack subs on-the-fly as you are looking at the target as long as your stars are reasonably focused and your sub-exposures show enough stars for alignment. (It is easy to see in the SharpCap log tab of the live stack window if subs are being stacked).

 

Collecting sub-exposures with SharpCap, and then later stacking them in DeepSkyStacker is a post-processing operation that, on CN, takes you into the realm of AP and traditional imaging, which is beyond the scope of the EAA forum.

 

Let us know if you intend to do EAA, or if you are looking to do traditional AP.


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#3 Gen166

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Posted 05 February 2023 - 03:55 PM

First of all, if you are doing EAA and using SharpCap, why are you not doing live stacking within SharpCap? SharpCap's live stack algorithm should automatically stack subs on-the-fly as you are looking at the target as long as your stars are reasonably focused and your sub-exposures show enough stars for alignment. (It is easy to see in the SharpCap log tab of the live stack window if subs are being stacked).

 

Collecting sub-exposures with SharpCap, and then later stacking them in DeepSkyStacker is a post-processing operation that, on CN, takes you into the realm of AP and traditional imaging, which is beyond the scope of the EAA forum.

 

Let us know if you intend to do EAA, or if you are looking to do traditional AP.

Thanks for the clarifying question: We are in fact live-stacking within SharpCap and it stacks the images fine.  The later stacking in DSS was simply an attempt to get better yield, since objects are only staying in FOV for 30 secs.

Didn’t mean to ask an AP question.

Right now what we’re getting just on SharpCap is mostly blurry blobs, and so I’m thinking we may have a distortion/focus problem.  That, or the chasing stuff across the frame is making this too hard for ourselves.



#4 JohnBear

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Posted 05 February 2023 - 04:54 PM

First - Welcome to CN!   welcome.gif

Have you made contact with a local astronomy club (we don't know where you are located yet, so update your CN profile when you get a chance).  Someone there will likely be glad to help you with an EAA setup,  

 

There are many, many arcane parameters in SharpCap that need to be set right (and done in a specific order) to get decent images = so that is not inherently intuitive.   Duplicating someone's existing setup is probably the easiest way to get started without a lot of initial frustration.  

 

The 'focus' issue can probably be resolved with some simple extermination.  If you are going to "enjoy" EAA then you will end up getting a tracking mount, but you wont need anything too esoteric or expensive.  

 

I am quite happy just using the rather simple and inexpensive Revolutiuon 2 imager system with small scopes on my SE or Evolution mounts.- but iI am not seeking Hubble like performance -  just something a bit better than what I can easily get with visual observing. 


Edited by JohnBear, 05 February 2023 - 04:56 PM.


#5 DarrylS

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Posted 05 February 2023 - 05:08 PM


 

B. Scope: We got the 102DX as a family toy a couple years ago.  It’s  F6.7 and FL is 660, so the camera FOV isn’t great (small sensor), but the platesolving bracket works pretty well, and we’re finding stuff fine.  It’s just … impossible to get crisp focus. (Yes, we’ve used a Bahtinov mask) Even when we leave the scope outside so it’s nice and adjusted to the temp.  Even the moon is fuzzy.  There’s also chromatic aberration, but that’s to be expected.  Is the dinky focuser our problem?  Any way to fix?  Or do we just need better glass?

 

C. Mount: Manual Alt-Az mount means we’re constantly chasing stuff across the field of view.  E.g. we tried shooting the Famous Comet and it would only stay in frame for about 30 seconds and then we’d have to move the scope, wait for the vibrations to settle down (about 5 secs) and start again.  I thought startracking wasn’t needed for EAA because you’re just doing short bursts anyway.  But would a Sky-Watcher Star Adventurer GTi change our results more than anything else?

Just to clarify, does the scope focus fine when you are just using it in visual mode (i.e. with an eyepiece)? If so, then that's one potential problem to eliminate.

 

When you try to focus with the ASIair, can you take it to both sides of focus -- that is, when you are trying to achieve focus can you tell that at a point you move from being underfocused then you are overfocused?  It would sort of be like a fuzzy blob getting smaller and smaller, then reversing and getting larger and larger. If you don't see that it may just be that you don't have enough back focus even with the diagonal.


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#6 BrentKnight

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Posted 05 February 2023 - 06:02 PM

A tracking mount would be the first thing I would get.  I would assume the blurry images are because your individual sub exposures are not aligning well.  This will cause fuzzy images.

 

The Sky-Watcher Star Adventurer GTi certainly looks like an appropriate mount if that's within the budget, but there might be cheaper alternatives as well.


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#7 star acres

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Posted 05 February 2023 - 06:08 PM

Could your lenses be smudgy?

#8 Gen166

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Posted 05 February 2023 - 07:47 PM

Many thanks for all the thoughts/questions/comments.  I think my take-away is that (a) no, there’s nothing so terrible about the SSE 102DX that it would doom our efforts on its own; and (b) we could probably do some more work to make sure we’re getting sharp clear focus.

 

To answer some of the questions: Yes, we are able to go “through” focus—from one side of focus out to the other, so it’s not a lack of focus range issue.  Frankly clarity through our eyepieces isn’t great, and of course the mount is flimsy enough that we can’t get up on the eyepieces.  The hope had been that substituting a good camera for the eyepiece would get us crystalline results that our eyes (and shivering little kid bodies) couldn’t quite manage.  (We’re in the mid Atlantic US, and it’s been cold.)

 

I’m going to find a helical focuser to see if that will help us dial in, and I think a proper tracking mount is the next investment priority.  Thank you for sharing your expertise!


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#9 Rickster

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Posted 05 February 2023 - 10:50 PM

Priority #1 is a tracking mount.


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#10 Tfer

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Posted 05 February 2023 - 11:29 PM

Your images are smeared because your mount doesn’t track. You stated that the comet crosses the FOV in 30 seconds.

Unless you’re taking 1/2 second exposures, your images will be smeared.

EAA allows the use of motorized ALT/AZ mounts, where traditional AP uses equatorial mounts exclusively. Your mount HAS to track the sky.

#11 BrentKnight

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Posted 06 February 2023 - 12:00 AM

Many thanks for all the thoughts/questions/comments.  I think my take-away is that (a) no, there’s nothing so terrible about the SSE 102DX that it would doom our efforts on its own; and (b) we could probably do some more work to make sure we’re getting sharp clear focus.

 

To answer some of the questions: Yes, we are able to go “through” focus—from one side of focus out to the other, so it’s not a lack of focus range issue.  Frankly clarity through our eyepieces isn’t great, and of course the mount is flimsy enough that we can’t get up on the eyepieces.  The hope had been that substituting a good camera for the eyepiece would get us crystalline results that our eyes (and shivering little kid bodies) couldn’t quite manage.  (We’re in the mid Atlantic US, and it’s been cold.)

 

I’m going to find a helical focuser to see if that will help us dial in, and I think a proper tracking mount is the next investment priority.  Thank you for sharing your expertise!

Curious why you would want a helical focuser?

 

It's almost a certainty that your "focus" problems are due to the non-tracking mount.  If your concerned that visually the focus isn't good either - you are expecting quite a lot from very inexpensive optics.  Instead of a new focuser, I'd consider new eyepieces.

 

As you say above, the SSE 102DX isn't terrible, but it's not great either.  Investing in a more capable mount will make a world of difference for EAA.  It will allow you to get good results with that refractor.  Unfortunately, getting a good tracking mount will make the StarSense obsolete as the mount itself will do the finding part. 

 

I'm not familiar with the telescope (OTA), but the core feature is always going to be the optics.  It does not make a lot of sense to spend resources on mechanicals like a new focuser when it's possible to spend a little more and get a better telescope (that will come with a better focuser).  If you don't want to go down that path, then stick with what you have and see how it works with a better mount (and some better eyepieces).


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#12 alphatripleplus

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Posted 06 February 2023 - 06:28 AM

Your images are smeared because your mount doesn’t track. You stated that the comet crosses the FOV in 30 seconds.

Unless you’re taking 1/2 second exposures, your images will be smeared.

EAA allows the use of motorized ALT/AZ mounts, where traditional AP uses equatorial mounts exclusively. Your mount HAS to track the sky.

+1

 

At the celestial equator stars have an apparent motion of 15 arcsec/second. Unless you have a very short focal length scope, a star (or comet) will be smeared over many pixels using a not tracking mount in a very short period of time.


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#13 YoYoYoMikey

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Posted 08 February 2023 - 09:12 AM

Have to agree with the get a mount opinions.  But something that has not been mentioned.  Take it out during the day and point at a static object, ideally over a mile away(cell tower)  How good is your focus now?  Also, do with the camera.  This will show you that the optics are good enough and you can actually get focus.  If this is the case you are back to the lack of tracking causing your blurring.  Mount it is.


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#14 Gen166

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Posted 19 February 2023 - 10:02 AM

Quick follow-up on this. Got a tracking mount which is great. Tried planetary shots and ... thinking I should look at a SCT or Newtonian for scope upgrade.
What is a better choice for planets (not deep space):
A 10" Newtonian/Dob at 1000mm and f4, or an SCT like a Celestron NexStar 8 at 2000mm and f10? I know the Celestron comes with a computerized mount etc. And I can use a Barlow to power up the 10" Newtonian.
What would be better for getting nice views of Jupiter Mars, Saturn rings...

#15 azcubs76

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Posted 19 February 2023 - 12:34 PM

Either of those telescopes would get good visual results for planets but the Dob would not be usable for EAA as it doesn't have tracking. The Celestron C8 which comes in the NexStar package is a very popular scope for EAA here on CN (I use one!) but the Nexstar mount gets tons of complaints. Many people happily use the higher quality Evolution or CPC mounts however.

 

There is currently no way to do moon/planetary EAA and we're not allowed to talk about the Lucky Imaging method here but tons of info in the Major & Minor Planetary Imaging forum so you should head over there. EAA is mainly used for viewing Deep Sky Objects (DSO) like nebula and galaxies. If you'd like info on EAA there are tons of experienced folks here eager to help out. 



#16 dave85374

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Posted 19 February 2023 - 12:41 PM

+1 on the Evolution mount



#17 alphatripleplus

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Posted 19 February 2023 - 12:53 PM

...tons of info in the Major & Minor Planetary Imaging forum so you should head over there. EAA is mainly used for viewing Deep Sky Objects (DSO) like nebula and galaxies. If you'd like info on EAA there are tons of experienced folks here eager to help out. 

+1 



#18 bostonsteve

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Posted 19 February 2023 - 02:53 PM

Two inexpensive things to buy which might help.

1. Bahtinov mask, this makes focusing much easier and you will be sure you got it right.

2. 0.5 focal reducer (I have a GSO brand). This will double your field of view.  Its not the best FR in the world, but for the cost I think it is worth it, especially starting out.

 

Each of these can be had for around $25

 

Start with big objects like Orion nebula or Andromeda galaxy, at low power they won't move out ov view very quickly.  As others suggested, use the sharpcap live stacking functionaliy.




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