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Beginner’s question on minimum subs exposure settings

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#1 Atriumglory

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Posted 24 September 2021 - 11:40 PM

Dear friends,

 

I am from Kuala Lumpur, Malaysia, totally new in telescope and Astro photography, but been seriously committed & spending money on this hobby since 2 months back, after accidentally saw Jupiter with its 4 moons, using my 20x80 binoculars (bought it a year ago but had never use it for night sky, instead been using it for terrestrial long distance viewing). That discovery of Jupiter had made me been so excited to see what else that I could find on the night sky.

 

Immediately, the next day on 21 July’21, I called up the store that sold me the binoculars, to ask for beginners’ telescope and bought 8” GSO dobsonian which made me even excited with the night sky objects. Could nicely see Jupiter, Saturn and many more stars. But was not feeling satisfied as I found it, so time consuming to manually and visually push the scope to find objects. Being a new person in this hobby, the immediate frustration was then…not knowing whether the star that the scope was pointing at, was the correct star that I tried to figure out via stellarium website and not able to ‘lock’ the objects long enough in the eyepiece… as the sky moves. Since the ‘accidental discovery’ of Jupiter.. I have been reading lots & watching YouTube for more informative and product reviews.

 

On 26 August’21, I received delivery of new telescope from B n H photo from New York to my house in Kuala Lumpur, Malaysia within 4 working days which was very fast (very reliable international store as I had ordered from them other products previously). I had to order from New York, as my local store in Malaysia had to back order and the same package will only be available in next 8-14 months due to global shortage & market manufacturing supply chain issues. 

 

I ordered a package from B n H photo, a Celestron 8” EdgeHD with CGEM II mount.  Been happy with it that I can now confidently identify the stars and the Nexstar’s Night Tour feature to see lots more objects.

 

Then on 15 September, I ordered ZWO 533MC-Pro, ZWO 120MC-s as guide camera, ZWO ASIAir Pro, ZWO Off axis guider, Optolong L-extreme and L-Pro filters and ZWO 2” filter drawer. 

 

My location is in city area, I presumed it is in bortle 7/8, capturing from above my roof top about 10 meters from the ground.

 

Been going through a very steep learning curve and many sleepless nights with very limited clear sky/short viewing window time/night (location here is very cloudy), to quickly understand how to use all these equipments. 

 

So far been on trial and errors to go through step by step to properly setup and understand how those equipments work with ASI AirPro.

 

Frankly speaking, I have yet to understand, what would be the reasonable settings, based on my above mentioned equipments, on the following (assuming trying to image M31):

1. The ‘minimum’ sub exposure time for my lights frames,

2. Given such a difficult sky with limited windows of between 2-3 hours/lucky clear sky night and thus far clear sky only happened once in 4-7 days (due to current raining seasons here), what would be my realistic deep sky targets ie. Focus on stars instead of nebula? Or will I still able to capture fair image of M31 for 2-3 hours of lights?

3. Thus far, I am no successful to link up my ASIAir Pro with USB connected to the bottom of the Nextstar+ hand controller to be able to use Goto function from ASIAir Pro.

4. As such, been guiding using on Camera ST4 from 120MC-s to CGEM II guide port. No issue with that ST-4 guide port setup and the mount Goto will slew to the object almost perfectly using the handcontroller, but the tracking when guiding, was not in synchronized with the target star as per crosshairs preview in ASIAir Pro. The images previewed / saved, under “Autorun” after each subs of 30 seconds, showed trails or oblong star.

5. Any settings that I need to pay particular attentions on ASIAir Pro and the CGEM II hand controller?

 

Truly appreciate any advice on the above.

 

Thank you


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#2 Atriumglory

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Posted 25 September 2021 - 12:03 AM

Optimized-376BBF3F-27E5-463F-9345-ED62EF3AEF38.png



#3 Atriumglory

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Posted 25 September 2021 - 12:09 AM

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#4 adosaj

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Posted 25 September 2021 - 12:20 AM

Have you polar aligned your mount? I think you are seeing the trails because of poor or no polar alignment of your setup. From your location, 30-60 second subs would be ideal, though you could try for longer and see how bright your sky background gets. I am in Bortels 9 and can get away with 5 minutes, but then have to deal with a heavy gradient. Also, I would use a mono camera for guiding since it would be more sensitive - no filter over individual pixels instead of the built in RGB filters that limit the light reaching your pixels. 
 

Anil



#5 Atriumglory

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Posted 25 September 2021 - 12:51 AM

Hi Adosaj,

 

yes.. I did polar align as well as all stars polar align using Nexstars hand controller. 

 

My location: 3*3’5”N and 101*45’20 E.

 

As CGEM II mount latitude is between 15-70*, I had to tilt the mount/scope forward to achieve that 3* latitude.

 

That night I used L-extreme filter (was lazy to change the filter to L-Pro…).



#6 adosaj

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Posted 25 September 2021 - 12:59 AM

Hi Adosaj,

 

yes.. I did polar align as well as all stars polar align using Nexstars hand controller. 

 

My location: 3*3’5”N and 101*45’20 E.

 

As CGEM II mount latitude is between 15-70*, I had to tilt the mount/scope forward to achieve that 3* latitude.

 

That night I used L-extreme filter (was lazy to change the filter to L-Pro…).

I don’t have experience with the CGEM, but I think you need to look in your manual for the mount to see if there is something special you need to do when using the mount a latitudes less than 15 degrees. Maybe someone who has this mount might be able to help you. A quick google search shows that you might need to use a custom wedge. 
 



#7 reglogge

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Posted 25 September 2021 - 01:13 AM

Dear friends,

 

I am from Kuala Lumpur, Malaysia, totally new in telescope and Astro photography, but been seriously committed & spending money on this hobby since 2 months back, after accidentally saw Jupiter with its 4 moons, using my 20x80 binoculars (bought it a year ago but had never use it for night sky, instead been using it for terrestrial long distance viewing). That discovery of Jupiter had made me been so excited to see what else that I could find on the night sky.

 

Immediately, the next day on 21 July’21, I called up the store that sold me the binoculars, to ask for beginners’ telescope and bought 8” GSO dobsonian which made me even excited with the night sky objects. Could nicely see Jupiter, Saturn and many more stars. But was not feeling satisfied as I found it, so time consuming to manually and visually push the scope to find objects. Being a new person in this hobby, the immediate frustration was then…not knowing whether the star that the scope was pointing at, was the correct star that I tried to figure out via stellarium website and not able to ‘lock’ the objects long enough in the eyepiece… as the sky moves. Since the ‘accidental discovery’ of Jupiter.. I have been reading lots & watching YouTube for more informative and product reviews.

 

On 26 August’21, I received delivery of new telescope from B n H photo from New York to my house in Kuala Lumpur, Malaysia within 4 working days which was very fast (very reliable international store as I had ordered from them other products previously). I had to order from New York, as my local store in Malaysia had to back order and the same package will only be available in next 8-14 months due to global shortage & market manufacturing supply chain issues. 

 

I ordered a package from B n H photo, a Celestron 8” EdgeHD with CGEM II mount.  Been happy with it that I can now confidently identify the stars and the Nexstar’s Night Tour feature to see lots more objects.

 

Then on 15 September, I ordered ZWO 533MC-Pro, ZWO 120MC-s as guide camera, ZWO ASIAir Pro, ZWO Off axis guider, Optolong L-extreme and L-Pro filters and ZWO 2” filter drawer. 

 

My location is in city area, I presumed it is in bortle 7/8, capturing from above my roof top about 10 meters from the ground.

 

Been going through a very steep learning curve and many sleepless nights with very limited clear sky/short viewing window time/night (location here is very cloudy), to quickly understand how to use all these equipments. 

 

So far been on trial and errors to go through step by step to properly setup and understand how those equipments work with ASI AirPro.

 

Frankly speaking, I have yet to understand, what would be the reasonable settings, based on my above mentioned equipments, on the following (assuming trying to image M31):

1. The ‘minimum’ sub exposure time for my lights frames,

2. Given such a difficult sky with limited windows of between 2-3 hours/lucky clear sky night and thus far clear sky only happened once in 4-7 days (due to current raining seasons here), what would be my realistic deep sky targets ie. Focus on stars instead of nebula? Or will I still able to capture fair image of M31 for 2-3 hours of lights?

3. Thus far, I am no successful to link up my ASIAir Pro with USB connected to the bottom of the Nextstar+ hand controller to be able to use Goto function from ASIAir Pro.

4. As such, been guiding using on Camera ST4 from 120MC-s to CGEM II guide port. No issue with that ST-4 guide port setup and the mount Goto will slew to the object almost perfectly using the handcontroller, but the tracking when guiding, was not in synchronized with the target star as per crosshairs preview in ASIAir Pro. The images previewed / saved, under “Autorun” after each subs of 30 seconds, showed trails or oblong star.

5. Any settings that I need to pay particular attentions on ASIAir Pro and the CGEM II hand controller?

 

Truly appreciate any advice on the above.

 

Thank you

A good way to calculate the optimal exposure time using the ASIAir Pro can be found here: https://eastwindastr...alculation.html
I also recommend reading through the other blog posts there to get very good and practical advice on how to get the most out of your ASIAir Pro.
If you are in a highly light polluted area, the best exposure time can be quite low, in the region of only seconds. Then you just have to take a *lot* of images.
Cheers, Reinhard



#8 Atriumglory

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Posted 25 September 2021 - 01:46 AM

I don’t have experience with the CGEM, but I think you need to look in your manual for the mount to see if there is something special you need to do when using the mount a latitudes less than 15 degrees. Maybe someone who has this mount might be able to help you. A quick google search shows that you might need to use a custom wedge. 
 

Thank you so much Adosaj… Preferably for that mount, I need to get a custom wedge.

 

And the quick solution is to tilt the original mount/tripod (bearing in mind to avoid it from falling down, need to sand bag the rear tripod legs / tie the mount rear legs, to the ground.



#9 Atriumglory

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Posted 25 September 2021 - 01:52 AM

A good way to calculate the optimal exposure time using the ASIAir Pro can be found here: https://eastwindastr...alculation.html
I also recommend reading through the other blog posts there to get very good and practical advice on how to get the most out of your ASIAir Pro.
If you are in a highly light polluted area, the best exposure time can be quite low, in the region of only seconds. Then you just have to take a *lot* of images.
Cheers, Reinhard

Hi Reglogge,

 

Happy to learn new thing from that article… at least now, I have some basis, on how to set the expo time based on the color ADU over the bias ADU. Will apply that technic in my next clear sky.. 

 

Thank you…



#10 Alex McConahay

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Posted 25 September 2021 - 08:55 AM

Your images show way too much trailing in 30 seconds to interpret the problem as polar alignment. A scope can be slightly out of polar alignment and still not show trailing like that. Polar MISalignment causes small arcs, nothing that big. And in 30 seconds, they would hardly be discernable. 

 

Does your scope track properly? That is, if you set it on a given target, does it stay there (on that target) for ten to fifteen minutes at a time. Does your target stay relatively centered? I should think with as much trailing as your exposures show in 30 seconds that the target would be off the frame. 

 

If you are in fact guiding, then you must not be guiding on a star. You could be guiding on a hot pixel in the guide camera. 

 

Even with a relatively long focal length scope, you are showing too much trailing. Something is wrong with your mount movement. 

 

Point your camera at something bright, like Jupiter or the moon. Something overhead, on the meridian/celestial equator or so. No need to be precise. Just something bright and easy to find. Use the liveview part of the planetary section of the ASI acquisition software. (That is, watch the target live on your screen.) Do not use autoguiding. The target should stay put on the screen. If it is moving, you must address why. Until you have it staying stationary on the screen, you cannot hope to do reasonable exposures. 

 

Alex



#11 adosaj

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Posted 25 September 2021 - 01:09 PM

Your images show way too much trailing in 30 seconds to interpret the problem as polar alignment. A scope can be slightly out of polar alignment and still not show trailing like that. Polar MISalignment causes small arcs, nothing that big. And in 30 seconds, they would hardly be discernable. 

At his focal length this is what I’d expect. I’ve seen large arcs at even 600-700mm FL when not properly polar aligned. The images are from his main imager not guide scope. 
 



#12 Atriumglory

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Posted 25 September 2021 - 07:23 PM

Your images show way too much trailing in 30 seconds to interpret the problem as polar alignment. A scope can be slightly out of polar alignment and still not show trailing like that. Polar MISalignment causes small arcs, nothing that big. And in 30 seconds, they would hardly be discernable. 

 

Does your scope track properly? That is, if you set it on a given target, does it stay there (on that target) for ten to fifteen minutes at a time. Does your target stay relatively centered? I should think with as much trailing as your exposures show in 30 seconds that the target would be off the frame. 

 

If you are in fact guiding, then you must not be guiding on a star. You could be guiding on a hot pixel in the guide camera. 

 

Even with a relatively long focal length scope, you are showing too much trailing. Something is wrong with your mount movement. 

 

Point your camera at something bright, like Jupiter or the moon. Something overhead, on the meridian/celestial equator or so. No need to be precise. Just something bright and easy to find. Use the liveview part of the planetary section of the ASI acquisition software. (That is, watch the target live on your screen.) Do not use autoguiding. The target should stay put on the screen. If it is moving, you must address why. Until you have it staying stationary on the screen, you cannot hope to do reasonable exposures. 

 

Alex

Hi Alex,

 

Those snapshots were taken from Main Camera ZWO 533MC-Pro

 

But, you are right…

 

the target object (star, moon, Jupiter) will slowly drift away from the crosshairs (using ASIAir Pro built in tool) when I view it through main camera with the mount on auto guiding. The target would be out from the crosshairs after 5-10 minutes.

 

Given the above, I would frequently press the Goto button on the hand controller to ‘re-slew’ it back to the center.

 

If you notice from those 2 sequential snapshot the trails are random… not in one particular direction.

 

Truly appreciate your view on the above.

 

AG



#13 Atriumglory

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Posted 25 September 2021 - 07:39 PM

At his focal length this is what I’d expect. I’ve seen large arcs at even 600-700mm FL when not properly polar aligned. The images are from his main imager not guide scope. 
 

 

Hi Adosaj,

 

Yes, those were taken from main camera ZWO 533MC-pro. 

 

While for auto guiding, I use 120MC-s with ZWO Off axis guider. Both main and guide camera are in focus as seen on ‘ASIAir preview mode’. 

 

Thank you..



#14 BinoGuy

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Posted 28 September 2021 - 06:15 PM

Welcome to the hobby!  

 

My two cents...

 

I think the star trails are from improper guiding.  I'd sort out the connection from the ASI to the mount first.  Head over to the equipment forum, I am certain someone with the ASI has your mount and can help you connect it.

 

After that go through the ASI AIR Pro polar alignment routine.  I find sometimes after I PA I turn it off and run through again and I can get a bit better.  Or 'more worsier'  (yeah, we have a complicated relationship)
 

Then, image without guiding and look at the results.  Even in KL you should be able to get 10 second subs.  Use the live stacking feature and see how things look and they stack.

 

The last thing I'll add is that footsteps can cause that effect sometimes too.  We were at a club event a week ago, and even on solid ground (baseball field grass behind 2nd base) and 3 feet of space between the tripod and me/viewers we could still see when people walked around when using longer subs.

 

 

good luck!
Clear skies, BG  °¿°


Edited by BinoGuy, 28 September 2021 - 06:15 PM.


#15 Atriumglory

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Posted 29 September 2021 - 02:50 AM

Hi Binoguy,

 

thank you on your reply. 
 

last night, I managed to do All stars and polar align using the procedures in the HC. For accuracy, I was doing the alignment using the direction control on the HC and the crosshairs tool in ASIAir Pro,  so that I could confirm each star was perfectly centered. Lastly, I did the same for PA alignment and adjust the mount respective knobs manually until the star was inside the crosshairs.

 

However, after spending more than 1 hour doing the above and making sure everything is perfectly tight and firmed, when I did the Preview in AAP, the star trails still visible, even at the exposure of 10 seconds.

 

The mount Goto is okay, as it could slew to the objects that selected in the HC.

 

It was the tracking that I still not able to get the right solution on what need to be done to rectify it.

 

The object would not stay put in the center of the crosshairs while guiding is ON… not even for 10 seconds though the trails were shorter, than those at 30 seconds.



#16 TelescopeGreg

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Posted 29 September 2021 - 11:40 AM

The images in the OP are what I would expect from an unguided scope.  At least, that's what mine looked like :)

 

As a test, if you take a dozen 30 second images and string them together in a movie or GIF, one second per image, you'll probably see something like these:

 

https://www.dropbox....le-M13.mp4?dl=0

https://www.dropbox....acking.mp4?dl=0

 

This was with an 8" f/5 (so, 1,000mm focal length) Newtonian on an AVX mount, unguided.  The OP's scope is longer than that, so the trails will be longer.

 

I'd check to be sure that your autoguiding is actually running, and that the guiding RMS is reasonable.  I suspect it's not.

 

To set expectations, when I finally did get guiding to work, I went from keeping one image in 10 to tossing one in 10, but that was still with only 20-30 second exposures.  Working on getting the scope's balance exactly right (it's harder than you think) and swapping equipment to a more compact setup (5" refractor, lighter guide scope), has resulted in my regularly taking 5 minute exposures (300 seconds) and keeping them all. 

 

The secret is keeping everything as light, short, and low as possible.  Guiding is an active process where the mount's motors are fighting the inertia of the scope on top, and inertia scales with mass, and the distance between the rotation axis and the mass SQUARED.  Squaring stuff makes small differences grow big really fast, so anything you can do to shrink the size of the scope will pay back big time.



#17 Atriumglory

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Posted 29 September 2021 - 07:04 PM

Hi TelescopeGreg,

 

Thank you for your reply.

 

I am very new to this Astro imaging. Have no one to learn from, at my location, aside from the current pandemic with mobility constraints and limited social activities. Have to do trials and errors.

 

As such will depend much on the advice from wonderful people like you in this forum.

 

You are right… Am thinking of getting a compact refractor too… been trying for so many nights and yet none could rectify the tracking problem.

 

I think, the 8” EdgeHD at 2030mm focal length, may not be ideal for CGEM II mount. Hopefully a lighter refractor would be much better tracking on the CGEM II.

 

Additionally, without a focal reducer the field of view is just too narrow and to me, it is not much of satisfaction for deep sky objects visual/imaging. Could not even capture the whole Pleiades. 

 

But one thing good, I still love the Goto feature of the CGEM II mount, which are very accurate and at that focal length, the far distance individual star/planet is very clear.



#18 Oort Cloud

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Posted 29 September 2021 - 07:18 PM

Hi TelescopeGreg,

Thank you for your reply.

I am very new to this Astro imaging. Have no one to learn from, at my location, aside from the current pandemic with mobility constraints and limited social activities. Have to do trials and errors.

As such will depend much on the advice from wonderful people like you in this forum.

You are right… Am thinking of getting a compact refractor too… been trying for so many nights and yet none could rectify the tracking problem.

I think, the 8” EdgeHD at 2030mm focal length, may not be ideal for CGEM II mount. Hopefully a lighter refractor would be much better tracking on the CGEM II.

Additionally, without a focal reducer the field of view is just too narrow and to me, it is not much of satisfaction for deep sky objects visual/imaging. Could not even capture the whole Pleiades.

But one thing good, I still love the Goto feature of the CGEM II mount, which are very accurate and at that focal length, the far distance individual star/planet is very clear.


Even with a reducer, I doubt an SCT could fit all of the pleiades...

It'll do a great job on globs, planets, and planetaries though! And The Crab :)

Not sure what typical seeing is like at your area, but those long focal lengths/image scales really do need better than average seeing though, maybe that's the issue...

I tried learning imaging on an SCT too; it's neither fun nor productive, which quickly led to me buying a refractor as well. I can manage with the SCT now though, but it was very tough in the beginning, and I only really get good results with it on the very best nights. The refractor, OTOH, yields good results in all but the worst skies.

#19 TelescopeGreg

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Posted 29 September 2021 - 09:24 PM

What Oort said. 

 

Deep Sky targets are surprisingly large, and often incredibly dim.  Most DSO imaging is done with focal lengths well below 1,000mm, many around 500mm or less.  I'm at 910mm, and a lot of targets are a tight fit.  You also want a faster scope, one with a focal ratio of f/7 or less.  Focal reducers help on both accounts.

 

A good 102mm f/7 scope will get you the vast majority of targets, and the wide-swath nebulae can be had with a 0.7x reducer / flattener (along with a nice fast f/5 speed) as an optional add-on.  Don't forget the guide scope and camera, watch the weight, and I expect your CGEM should be able to handle it.



#20 Atriumglory

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Posted 30 September 2021 - 05:18 AM

Even with a reducer, I doubt an SCT could fit all of the pleiades...

It'll do a great job on globs, planets, and planetaries though! And The Crab smile.gif

Not sure what typical seeing is like at your area, but those long focal lengths/image scales really do need better than average seeing though, maybe that's the issue...

I tried learning imaging on an SCT too; it's neither fun nor productive, which quickly led to me buying a refractor as well. I can manage with the SCT now though, but it was very tough in the beginning, and I only really get good results with it on the very best nights. The refractor, OTOH, yields good results in all but the worst skies.

Hi Oort,

 

I am staying in bortle 7/8 area. Having had so many frustrated nights with the guiding. 

Am thinking of selling my 1 month old EdgeHD and get a compact refractor. 

 

Thanks for sharing your experience on SCT during the early days.



#21 Atriumglory

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Posted 30 September 2021 - 05:28 AM

What Oort said. 

 

Deep Sky targets are surprisingly large, and often incredibly dim.  Most DSO imaging is done with focal lengths well below 1,000mm, many around 500mm or less.  I'm at 910mm, and a lot of targets are a tight fit.  You also want a faster scope, one with a focal ratio of f/7 or less.  Focal reducers help on both accounts.

 

A good 102mm f/7 scope will get you the vast majority of targets, and the wide-swath nebulae can be had with a 0.7x reducer / flattener (along with a nice fast f/5 speed) as an optional add-on.  Don't forget the guide scope and camera, watch the weight, and I expect your CGEM should be able to handle it.

Hi Greg

 

I am seriously exploring to get such short focal length refractor with fast f ratio.

 

I made a wrong buying decision of getting the 8" EdgeHD premised on misunderstanding that long focal length would be good for deep sky and 'night space walking'. Though no doubt , the EdgeHD is good in getting a close up visual of the objects.

 

Thank you for the reply and advise, Greg



#22 Oort Cloud

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Posted 30 September 2021 - 06:44 AM

Hi Greg

I am seriously exploring to get such short focal length refractor with fast f ratio.

I made a wrong buying decision of getting the 8" EdgeHD premised on misunderstanding that long focal length would be good for deep sky and 'night space walking'. Though no doubt , the EdgeHD is good in getting a close up visual of the objects.

Thank you for the reply and advise, Greg


If you can afford to, I'd consider keeping the edge until you learn the ropes. It's by no means impossible to image with; it's just difficult to learn on. If you need to sell it to finance the purchase of a more appropriate AP scope, then by all means, that is probably the best choice.

#23 sbharrat

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Posted 30 September 2021 - 07:31 AM

Hi Greg

 

I am seriously exploring to get such short focal length refractor with fast f ratio.

 

I made a wrong buying decision of getting the 8" EdgeHD premised on misunderstanding that long focal length would be good for deep sky and 'night space walking'. Though no doubt , the EdgeHD is good in getting a close up visual of the objects.

 

Thank you for the reply and advise, Greg

 

If you can afford to, I'd consider keeping the edge until you learn the ropes. It's by no means impossible to image with; it's just difficult to learn on. If you need to sell it to finance the purchase of a more appropriate AP scope, then by all means, that is probably the best choice.

+1 to Oort. You of course know what you can afford and it is DEFINITELY easier to start with a small refractor (mine is 480FL, 80mm aperature). But you will get to a point where you are going to want that EdgeHD for galaxies. So if budget absolutely only allows one, then replace with small refractor. But if you can afford to have the Edge "sit in storage" for a year, you will eventually need it. 


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#24 TelescopeGreg

TelescopeGreg

    Soyuz

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Posted 30 September 2021 - 10:22 AM

+1 to Oort. You of course know what you can afford and it is DEFINITELY easier to start with a small refractor (mine is 480FL, 80mm aperature). But you will get to a point where you are going to want that EdgeHD for galaxies. So if budget absolutely only allows one, then replace with small refractor. But if you can afford to have the Edge "sit in storage" for a year, you will eventually need it. 

Another option might be the Hyperstar attachment for the EdgeHD scope.  That will take the scope down to 390mm focal length and a blazingly fast  f/2.  The only stretch might be the mount, as it will add another 2lbs to the already large scope.  I don't know the limits of what your mount can handle when carefully balanced and guided. 

 

The EdgeHD is a nice scope for visual work.  It would be a shame to trade it in, as there's still something magical in having million-year-old photons land on your retina.



#25 sbharrat

sbharrat

    Apollo

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Posted 30 September 2021 - 10:33 AM

Another option might be the Hyperstar attachment for the EdgeHD scope.  That will take the scope down to 390mm focal length and a blazingly fast  f/2.  The only stretch might be the mount, as it will add another 2lbs to the already large scope.  I don't know the limits of what your mount can handle when carefully balanced and guided. 

 

The EdgeHD is a nice scope for visual work.  It would be a shame to trade it in, as there's still something magical in having million-year-old photons land on your retina.

Umm. If the goal is to get the OP something that is easy to learn AP on, then an F2 scope would probably not be recommended lol.gif


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