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Want to start guiding, but how?

Beginner CMOS DSO EQ Equipment Imaging Polar Alignment Refractor Accessories
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9 replies to this topic

#1 mchriste

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Posted 12 May 2021 - 07:29 AM

Hi all, I have been thinking a long time about what to put in this post, because 1) I have a million questions and 2) I have a tendency to overcomplicate things!

 

I started out last year. As soon as I got an astrocamera with the idea of doing some EAA, I've been bit pretty hard by the AP bug. In fact my wife complained the other day that "we never look at the stars anymore!" since I'm staring at - and cursing at - my laptop instead. Anyway, I'm thinking about converting to a small guided EQ setup in hopes of getting sharper DSO images.

Current setup (details in sig): 72ED refractor (2.1 kg), SW AZGti mount on a photo tripod, IMX385-based camera. Gives me FOV 0.96° x 0.54°, 1.79"/pixel (rather a bit under- than oversampled)

 

Main challenges I'm facing: I only have a clear view of the sky in a Southern direction (pretty much 90° to 270°, i.e. E-S-W) and my telescope is a rather strange "hybrid" that must be mounted using a Vixen-compatible "foot" (no rings).

 

Fundamental question first: is it even possible to polar align under these conditions?
"Not being able to see Polaris" is one thing, but not being able to see any part of the northern sky is a different ballgame! As an experiment I tried to place the mount on a fluid video head (not geared) and align "freestyle" using the Synscan polar alignment routine as well as the drift method. I utterly failed twice, but is it because I didn't have a proper wedge or because it just can't be done from a south-facing location? If the latter, I'd rather stop right here.

 

Here's what I'm thinking of buying:
EQ "wedge": Benro GD3WH (based on the good opinions I read in this thread)
Dovetail (for side-by-side setup): TS Guidemount
Power/control: i-tec USB 3.0 Charging HUB 7-port 36W (I'm running 3 cables from the scope: USB + EQMOD to laptop, 12v to AC)
Guide scope: SvBony SV165 (120/30mm f/4) or SvBony SV106 (190/50mm f3.8)
Guide Camera: SV105 or ZWO ASI120MM Mini or ZWO ASI290MM Mini

 

And here are the predictable concerns and questions (beyond the fundamental one above):

Weight: total (depending on guidescope) will be ~3.0 to 3.4 kg. AZGti weighs 1.3kg. Counterweights, I have 1kg and 2kg. GD3WH is rated for 6kg, should I be worried? (I'll be at at the limit with CW). My RT75C tripod can supposedly carry 20kg - I have my doubts about that value but still I think I should be OK.

 

Guide scope: which one? Am I asking for trouble by trying to attach the 190/50 on that Guidemount clamp? (flexing!) Also, what's more important, light collection or larger FOV? (i.e. more "dimmer" stars or fewer "brighter" ones)

 

Camera: which one? (or another one altogether? The ASI174 is really expensive...) Thoughts about my choices:

 

SV105 (on 120/30: 5.15° x 1.83°, 5.15"/px; on 190/50: 1.73° x 1.16°, 3.25"/px)
Why? Price of course, plus wider FOV and better resolution than ASI120MM!

However, it's OSC and apparently only max. 500ms (can't this be hacked?). Would that be "good enough" for my setup?

 

ASI120MM (on 120/30: 2.29° x 1.72°, 6.44"/px; on 190/50: 1.45° x 1.08°, 4.07"/px)
Currently my favorite. I am contemplating the Mini rather than the -S; my 385 is already a very fast planetary camera so why USB3. Thoughts?

 

ASI290MM (on 120/30: 2.68° x 1.52°, 4.98"/px; on 190/50: 1.69° x 0.96°, 3.14"/px)
Seems a bit overkill to me. However, could I potentially use it to collect additional Luminance data (maybe Ha) on planets or even DSO (if I swap and guide with

ASI385)? Otherwise, what would the extra 100.- really get me in my specific situation?

 

Also, I am hoping that within a year or so I'll have access to more open spaces and darker (maybe Bortle 5) skies. I dream of upgrading at that point to something larger and better, and put say 10k into a 8" to 10" SCT or RC with a good mount and a cooled camera. I'm only mentioning this here because my plan would then be to recycle my 385 camera for guiding (OAG, or perhaps with the 72ED as guide scope). Is this viable? Since the stuff I'm buying now would pretty much only be used for this smaller setup, I prefer to save more for later rather than get too fancy here...

 

What would you do in my stead? (Or would my money be better spent on a larger camera and a field flattener? I already have a good bridge camera (Lumix FZ1000) so I'm not keen on getting a DSLR at the moment...)

 

 

And few bonus questions wink.gif

Naive question of the day: why don't they make "hybrid" mono AND color cameras? i.e. by placing the Bayer mask on some kind of flip mechanism to switch from one to the other. I'm not an engineer so maybe this is a stupid idea...

 

I'm attaching an image of M81 that I obtained in Alt-AZ without guiding from a Bortle 5 sky (obviously not from home). However, I feel a bit guilty: I think I processed it so hard (cf raw stack) that it's simply "cheating" at this point! (stacked FITS and details available here) Thoughts?

 

Is this about in line what I can expect with my setup, or should I just practice more rather than spend more money at this point? lol.gif

Attached Thumbnails

  • M81_processed..jpg
  • M81_stretched_stack..jpg


#2 idclimber

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Posted 12 May 2021 - 08:52 AM

Forget camera upgrades, you need a good mount. IMHO you have reached if not exceeded the limits of what you have. As a minimum an EG6-R would be my suggestion.



#3 Hypoxic

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Posted 12 May 2021 - 09:59 AM

Agree. I upgraded to an EQ6-R mount (choose your own upgrade of course) and downloaded PHD2, a very mild learning curve involved there, which took my imaging to the next level. Many CN members helped me through the initial trial and error phases of PHD2 but now, combined with a lot of reading here, I have a decent grip on guiding.

 

I have the ZWO ASI290mini and it works very well for me with a TS 50mm guide scope on a TS SD-APO 72mm APO.

 

I only mention this because I see you linked TS in your post. TS is a good shop, I stand by them 100% and order 90% of my gear through them. They do honest business and work with you if you have problems. They may take a few days to respond to emails (each time) but they always do respond, keep in mind though that they are a very busy shop. I had an APO telescope with tilt issues. After several email exchanges (a couple/few weeks total) to troubleshoot the problem on my end (normal), they took the APO back. About a month passed and they sent me an email stating that they had tested the APO on their end and found it to be defective, and replaced it. The new APO has been great. Treat them respectfully and you'll get good results, you just need to be a little patient, especially now with the COVID situation in Europe, they may be running minimal staff. They're good people at TS and I trust them.

Attached Thumbnails

  • Scope.jpeg

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#4 audioengr

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Posted 12 May 2021 - 12:49 PM

The small ZWO guidescope combined with the ASI120mm camera should work well for you and it's inexpensive.

 

I use the 120mm camera with the ZWO 60mm guidescope.  I made my own dew-shield for it using flexible magnetic sheeting.

 

Make sure you do a good job of calibrating the mount to the guidescope using PHD2.  I like to calibrate for each new object, even though they say it's best to calibrate to a star about 20 degrees above the horizon.  Seems to work well for me.


Edited by audioengr, 12 May 2021 - 12:49 PM.


#5 stargzr66207

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Posted 12 May 2021 - 06:00 PM

Martin,

idClimber and Hypoxic have it RIGHT!  If you are going to get into long exposure guided astrophotography, the foundation for success is a solid mount that is rock steady and tracks accurately. Without meeting these requirements, all of your efforts will end in frustration. My suggestion is to get a good German Equatorial mount with a load capacity that is at least TWICE what your equipment will weigh.

 

Ron Abbott



#6 JCDAstro

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Posted 12 May 2021 - 09:02 PM

I started out last year. As soon as I got an astrocamera with the idea of doing some EAA, I've been bit pretty hard by the AP bug. In fact my wife complained the other day that "we never look at the stars anymore!" since I'm staring at - and cursing at - my laptop instead.

Same thing happened to me, so I bought a Baader Flip Mirror II and have eyepieces configured with par-focal rings.  You can switch between the eyepiece to look at the stars and also the camera to take a long exposure for EAA.  Recently i added the optional Off-axis guider and a ZWO ASI290MM.  This has been working for me quite well, though learning the OAG took me some time, i had an easier time starting to guide with a guide scope piggybacked on my refractor to be honest, but i like the ability of the Flip mirror to do visual as I have a number of nice EPs.

 

https://www.baader-p...r-diagonal.html



#7 mchriste

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Posted 15 May 2021 - 07:58 AM

Thank you for your replies. I don't want to sound ungrateful, but I confess myself a little bit disappointed because I don't think my questions have been answered... idea.gif

 

To address the elephant in the room: Yes, I am fully aware that my mount is limited. However, something bigger/heavier is just not an option in my current surroundings (I observe from a 2m x 1.50 m balcony and have very little storage space in the apartment). I was originally thinking of a CEM25p but finally decided that already this was too heavy/clunky. I also know about the harmonic drive mounts (e.g. RST135) but frankly they are way too much money in view of my mid-term plans. Like I said, I'd rather save up and upgrade to a serious mid-range mount once I have more room - something like a CEM70 or Losmandy G11. Buy once, cry once and all that. But that's not the point of my questions in this thread. I'm just wondering whether I could noticeably improve my setup for a couple hundred $$ (even if I'm aware it won't be "perfect") or if it's a complete waste because I won't be able to polar align no matter what I do. From the Skywatcher AZGTi thread it seems to me that people have been quite successful in doing EQ-astrophotography (all limitations considered). There's also discussion that this little mount works much better guided than unguided - hence my motivation.

 

Note that regardless of the mount involved, my main questions still apply:

1) is it possible to polar align without seeing ANYTHING towards North? (nothing between 270° to 90° - my balcony faces South!)

2) is it viable to place a "larger" guide scope on a clamp for side-by-side mounting, retained only by a single screw, or would it flex too much?

 

@audioengr are you using a "side-by-side" setup or is your guidescope attached to the main scope with two separated rings?

 

I guess I should have posted my questions in separate threads with more meaningful titles. Maybe I'll still do it if that's ok with the rules...

 

Thanks! flowerred.gif



#8 RogeZ

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Posted 15 May 2021 - 08:04 AM

Basically you are not doing AP, you are doing EAA. Thats fine and produces fun results.

With that in mind, a 290MM is much more sensitive, mono and will help gather more signal within the limitations.

And yes, you can polar align, look for Drift Alignment.

#9 kathyastro

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Posted 15 May 2021 - 08:12 AM

I agree with the others that a mount should be a priority. 

 

To answer your question about polar aligning, yes it is possible to polar align quite accurately without seeing north.  You roughly align the azimuth of the mount using a compass (corrected for magnetic variation).  Set the elevation of the wedge with an inclinometer.  Then you perform a drift alignment or a star in the east and a star in the south.  That will give you an accurate polar alignment.

 

Any connection using a single screw will flex.  It may be better than nothing, but it will eventually frustrate you.



#10 pedxing

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Posted 15 May 2021 - 01:25 PM

I imaged for several years from a location where the view to the north was blocked. You get good at drift aligning pretty quickly. It's not as easy as direct polar alignment, but definitely viable.




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