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CGEM 8 EdgeHD vs CGEM 9.25


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These both come in at the same exact price and I found them in stock. Anyone familiar with either? Just want to understand what would drive you to choose one over the other.

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Depends on what you wanted to use it for.

For me:

Planetary and lunar visual or imaging  = C9.25 (the extra aperture helps here).

Deep sky visual or imaging = C8 EdgeHD (the wide corrected field and shorter focal length helps here).

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7 hours ago, CraigT82 said:

Depends on what you wanted to use it for.

For me:

Planetary and lunar visual or imaging  = C9.25 (the extra aperture helps here).

Deep sky visual or imaging = C8 EdgeHD (the wide corrected field and shorter focal length helps here).

Thanks so much, and I see what you're saying.  Would the C9.25 also be able to handle some DSO?  I'm not talking anything complex or obscure etc, just light DSO work.  I understand I would probably need a focal reducer for it so no big deal, I'm not trying to wow the world here I just want to be engaged in the hobby for some nice pics every now and again.

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It is not really a case of can the scope handle it.... it more of a question of can the user handle it!

Pretty much any scope can be used for DSO photography and the sheer variety of astronomical objects out there, of varying sizes and brightness', means that whilst that no one scope is the best for every object there are good scopes for some objects and good scopes for other objects.

For example, a little 80mm f/5 refractor with it's short focal length is good for large objects like the Andromeda galaxy and the Orion nebula, but not so good for small objects like small galaxies or planetary nebula.

A big SCT like the C9.25 has a decent aperture and a long focal length, this makes it good for imaging distant, small galaxies and planetary nebula, but also for getting up close and personal to details in the larger dust and cloud complexes.

The kicker is that generally speaking, the longer the focal length the more precise the tracking has to be. This means that it is much more difficult to get good* images with the long FL SCT than with the short FL refractor. Also the design of the SCT can make it difficult as it has a moving mirror focusing system which can cause problems with guiding, and also it requires collimation.

So basically what I'm saying is yes you can get amazing deep sky images from a C9.25, but you really have to know what you're doing.

Here is an image made by someone using a C9.25 on a CGEM mount, this person knows what they are doing though and probably has a lot of imaging time under their belt, so don't expect to get images like this right off the bat... https://www.astrobin.com/37198/?nc=user 

*of course the definition of a 'good' image is purely subjective and differs greatly from person to person. 

 

 

 

 

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Invaluable information here, thank you for taking your time to detail all that out for me and showing me an example of what can be achieved and the limitations.  I don't expect to automatically produce amazing quality work off the bat and it's something I will have to learn in time.  I wish I could say I was the young kid with the cool scope mom & dad got me for Christmas one year and I've used it ever since etc etc.  But that wasn't me sadly...I'm only getting into all of this now that I'm getting to be middle-aged and I don't have the time to invest in a starter scope and keep upgrading upgrading upgrading. With young kids it's simply not an option right and if I wait any longer I'll be old and gray lol.

I do appreciate all the insight.

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BTW, the 8" EdgeHD is no slouch on planets and the moon either. I have the classic C8, and it gives great results on the planets, moon and sun, but in terms of guiding, even with a focal reducer (0.63x) it is quite a handful. Most of my DSO imaging is with either a 80 mm F/6 triplet with 0.8x focal reducer, or my Meade 6" F/5 Schmidt Newton. I am getting a Starizona Night Owl 0.4x  reducer (for regular SCTs, not the EdgeHDs), and that brings the scope down to a more manageable 800 mm focal length at F/4. The image circle is only 16 mm however, but that fits my ASI183MM camera precisely. That reducer is not suitable for DSLRs.

If planets are your passion, however, the C9.25 has the edge

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25 minutes ago, michael.h.f.wilkinson said:

BTW, the 8" EdgeHD is no slouch on planets and the moon either. I have the classic C8, and it gives great results on the planets, moon and sun, but in terms of guiding, even with a focal reducer (0.63x) it is quite a handful. Most of my DSO imaging is with either a 80 mm F/6 triplet with 0.8x focal reducer, or my Meade 6" F/5 Schmidt Newton. I am getting a Starizona Night Owl 0.4x  reducer (for regular SCTs, not the EdgeHDs), and that brings the scope down to a more manageable 800 mm focal length at F/4. The image circle is only 16 mm however, but that fits my ASI183MM camera precisely. That reducer is not suitable for DSLRs.

If planets are your passion, however, the C9.25 has the edge

It's such a difficult decision and I keep going back and forth between CGEM and AVX in both aperture sizes.  Back and forth, back and forth I go.  I feel like that means even with all the research I've done I'm somehow still not ready to pull any trigger, and my better judgment is telling me to slow down again.  Kind of frustrating and confusing to be honest, I almost can't remember what's what anymore and am having trouble making a clear decision.  Probably not the best mode for buying something expensive lol.

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Just now, Maideneer said:

It's such a difficult decision and I keep going back and forth between CGEM and AVX in both aperture sizes.  Back and forth, back and forth I go.  I feel like that means even with all the research I've done I'm somehow still not ready to pull any trigger, and my better judgment is telling me to slow down again.  Kind of frustrating and confusing to be honest, I almost can't remember what's what anymore and am having trouble making a clear decision.  Probably not the best mode for buying something expensive lol.

For imaging, I think the CGEM has a clear advantage, especially with the heavier OTA of the C9.25 (considerably heavier than the C8). Note that you can always put others scopes on the mount. Planetary and lunar imaging are a lot easier to master than DSO, and are a lot quicker in practice, because you don't need hours of exposure time. I have been using my C8 on its Vixen Great Polaris mount for planetary imaging for a long time before getting a smaller scope (80mm F/6 triplet) to start doing DSOs. You can always first get the C9.25, which is outstanding for planets, both photographically and visuall, and great for DSOs visually, and add a DSO imaging scope (or two ;) ) later. To get an idea of what a C8 can do on planets, here is one of my best planetary shots (when Jupiter was a lot higher in the sky, I should add):

JupiterContrastSatBoosted.jpg.6f76580d2f18404f6302e550c72a7d56.jpg

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4 hours ago, CraigT82 said:

It is not really a case of can the scope handle it.... it more of a question of can the user handle it!

Pretty much any scope can be used for DSO photography and the sheer variety of astronomical objects out there, of varying sizes and brightness', means that whilst that no one scope is the best for every object there are good scopes for some objects and good scopes for other objects.

For example, a little 80mm f/5 refractor with it's short focal length is good for large objects like the Andromeda galaxy and the Orion nebula, but not so good for small objects like small galaxies or planetary nebula.

A big SCT like the C9.25 has a decent aperture and a long focal length, this makes it good for imaging distant, small galaxies and planetary nebula, but also for getting up close and personal to details in the larger dust and cloud complexes.

The kicker is that generally speaking, the longer the focal length the more precise the tracking has to be. This means that it is much more difficult to get good* images with the long FL SCT than with the short FL refractor. Also the design of the SCT can make it difficult as it has a moving mirror focusing system which can cause problems with guiding, and also it requires collimation.

So basically what I'm saying is yes you can get amazing deep sky images from a C9.25, but you really have to know what you're doing.

Here is an image made by someone using a C9.25 on a CGEM mount, this person knows what they are doing though and probably has a lot of imaging time under their belt, so don't expect to get images like this right off the bat... https://www.astrobin.com/37198/?nc=user 

*of course the definition of a 'good' image is purely subjective and differs greatly from person to person. 

 

 

 

 

I agree with the thrust of your post but would argue that you don't need a very long focal length any more for small galaxies. Pixels have also become smaller. This M51 was taken with a 140mm refractor with a focal length of just over a metre.

https://www.astrobin.com/342334/?nc=user

Olly

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1 hour ago, michael.h.f.wilkinson said:

For imaging, I think the CGEM has a clear advantage, especially with the heavier OTA of the C9.25 (considerably heavier than the C8). Note that you can always put others scopes on the mount. Planetary and lunar imaging are a lot easier to master than DSO, and are a lot quicker in practice, because you don't need hours of exposure time. I have been using my C8 on its Vixen Great Polaris mount for planetary imaging for a long time before getting a smaller scope (80mm F/6 triplet) to start doing DSOs. You can always first get the C9.25, which is outstanding for planets, both photographically and visuall, and great for DSOs visually, and add a DSO imaging scope (or two ;) ) later. To get an idea of what a C8 can do on planets, here is one of my best planetary shots (when Jupiter was a lot higher in the sky, I should add):

JupiterContrastSatBoosted.jpg.6f76580d2f18404f6302e550c72a7d56.jpg

That's an amazing image, wonderful job!  I've heard that regardless of scope, the supplied eyepieces aren't going to cut it and I should grab something additional...any recommendations?  Also, having trouble figuring out the difference between StarSense vs CPWI vs ASPA vs whatever else lol.  It's just not sticking in my head for whatever reason...probably because I just had my 2nd Covid shot and it's beating me up right now.

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Just now, Maideneer said:

That's an amazing image, wonderful job!  I've heard that regardless of scope, the supplied eyepieces aren't going to cut it and I should grab something additional...any recommendations?  Also, having trouble figuring out the difference between StarSense vs CPWI vs ASPA vs whatever else lol.  It's just not sticking in my head for whatever reason...probably because I just had my 2nd Covid shot and it's beating me up right now.

For imaging, the eyepieces don't really play a role. In that image, as I recall, I used a 2x TeleXtender and ASI224MC camera. Right now I would probably go for the ASI183MC without additional optics. Visually, eyepieces can certainly make a difference, but at F/10 the SCT or EdgeHD scopes aren't picky. Simple Plossl designs will work well (I used them for a long time, before switching to something more expensive). I think these scopes come with something like a 25mm Plossl, which is a pretty decent EP to start with. For planets, a few EPs around the 10mm mark would be useful. If you can take the  short eye relief, Plossls and orthoscopics are fine at the shorter focal lengths for planets. I cannot stand the short eye relief, so would opt for something like the Vixen SLVs, the Pentax XFs (not that expensive, but only available in 12mm and 8.5mm). If you want to splash out, Pentax XWs and Tele-Vue Delos EPs are great, and offer a much wider FOV. Be sure to read this post before spending:

 

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Posted (edited)

If you aim at astrophotography including deep space (not only planets which will be in the center of the image field) I would without doubt chose the EdgeHD8 since it has superior optics with a flat field. No brainer to me. The 9.25 is a planetary and visual instrument that lacks the extra lenses needed to give a wider flat field. The 9.25 will catch 33% more photons, which is not much, and then you can catch those by just exposing 33% longer with the EdgeHD and have nicely shaped stars all over the image. Also the 8" scope weighs 3 kg less, so easier to handle for the mount.

EDIT: The longer focal length of the 9.25 makes it even less useful for deep space.

Edited by gorann
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2 minutes ago, gorann said:

If you aim at astrophotography including deep space (not only planets which will be in the center of the image field) I would without doubt chose the EdgeHD8 since it has superior optics with a flat field. No brainer to me. The 9.25 is a planetary and visual instrument that lacks the extra lenses needed to give a wider flat field. The 9.25 will catch 33% more photons, which is not much, and then you can catch those by just exposing 33% longer with the EdgeHD and have nicely shaped stars all over the image. Also the 8" scope weighs 3 kg less, so easier to handle for the mount.

But personally I would not start with an 8" F/10 scope for DSOs. Not easy to guide, and long exposures are required.  The reducers (typically 0.7x) for the EdgeHD scopes are far more expensive than the 0.63x reducer/corrector of the SCTs, and even the Starizona 0.4x reducer is cheaper.  The 0.63x give pretty decent correction over an APS-C sensor, and the 0.4x appears to be well corrected for an ASI183-size sensor.

 

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19 minutes ago, michael.h.f.wilkinson said:

But personally I would not start with an 8" F/10 scope for DSOs. Not easy to guide, and long exposures are required.  The reducers (typically 0.7x) for the EdgeHD scopes are far more expensive than the 0.63x reducer/corrector of the SCTs, and even the Starizona 0.4x reducer is cheaper.  The 0.63x give pretty decent correction over an APS-C sensor, and the 0.4x appears to be well corrected for an ASI183-size sensor.

 

The reducer for the EdgeHD8 has gone down in price compared to what I once paied for it, I see that FLO sells it for 389 pounds, and it will give a perfectly flat field. The cheaper reducers may also introduce chromatic aberrationn (stars that are blue on one side and red on the other), at least that is my experience.

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1 hour ago, ollypenrice said:

So the real question might be, Why go for either as a deep sky imaging scope and especially a first one? Goran? Michael? I wonder what you think.

Olly

I would happily go for either as a first, all-round visual and planetary and lunar imaging scope. I got my C8 over 25 years ago, and never regretted buying it. It is compact, has nice aperture, travels well, holds collimation as a rock. For DSO imaging, and wide-field views, the APM 80 mm F/6 triplet with reducer/flattener is way better. 

Then there are Mak-Newts. These can provide aperture enough for lunar and planetary, and are fast enough for DSO imaging. Heavier than the corresponding SCT. If I didn't already have a 6" Schmidt-Newton, I would certainly be considering a Mak-Newt. 

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1 hour ago, ollypenrice said:

So the real question might be, Why go for either as a deep sky imaging scope and especially a first one? Goran? Michael? I wonder what you think.

Olly

 

30 minutes ago, michael.h.f.wilkinson said:

I would happily go for either as a first, all-round visual and planetary and lunar imaging scope. I got my C8 over 25 years ago, and never regretted buying it. It is compact, has nice aperture, travels well, holds collimation as a rock. For DSO imaging, and wide-field views, the APM 80 mm F/6 triplet with reducer/flattener is way better. 

Then there are Mak-Newts. These can provide aperture enough for lunar and planetary, and are fast enough for DSO imaging. Heavier than the corresponding SCT. If I didn't already have a 6" Schmidt-Newton, I would certainly be considering a Mak-Newt. 

As we know there is no single scope for everything, but the OPs mindset seems to be for a 8 - 9" SCT. He could then later get something else for more wide field work (a small refractor or why not a RASA8).

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This has been helpful y'all.  Like I said, I'm not going to probably ever go hardcore DSO AP, just want something for light work eventually.  Yes I can eventually grab something else if I so choose, who knows...the technology might improve in the next 5 years.

Anyway, I think I am going to go for the 8" Edge HD AVX.  That seems to be a nice sweet spot for a lot of things.  Can someone tell me if this set-up would work or if there are things you would include/exclude?

  • Advanced VX 8" EdgeHD Telescope
  • DEW SHIELD DX FOR C6 & C8

  • STARSENSE AUTOALIGN

  • NEUTRAL DENSITY MOON FILTER - 1.25"

  • 8-24MM ZOOM EYEPIECE - 1.25"

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Good choice! The rest seems fine too except I have no idea what Starsence Autoalign is but someone else here may have a comment on that.

The very best of clear skies to you!, I bet you will be excited pressing the buy button!

Göran

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21 hours ago, Maideneer said:

This has been helpful y'all.  Like I said, I'm not going to probably ever go hardcore DSO AP, just want something for light work eventually.  Yes I can eventually grab something else if I so choose, who knows...the technology might improve in the next 5 years.

Anyway, I think I am going to go for the 8" Edge HD AVX.  That seems to be a nice sweet spot for a lot of things.  Can someone tell me if this set-up would work or if there are things you would include/exclude?

  • Advanced VX 8" EdgeHD Telescope
  • DEW SHIELD DX FOR C6 & C8

  • STARSENSE AUTOALIGN

  • NEUTRAL DENSITY MOON FILTER - 1.25"

  • 8-24MM ZOOM EYEPIECE - 1.25"

I might add in the reducer and possibly a better finder. But looks like my buying list! 

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1 hour ago, philtodd said:

I might add in the reducer and possibly a better finder. But looks like my buying list! 

I think I'm gonna wait on a reducer because I'll think about getting a Hyperstar which I am reading does a fantastic job and I also have to think about a proper camera.  Right now I'm going to solely focus (ha) on visuals for a while so I can get familiar and acclimated to everything.

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23 hours ago, Maideneer said:

This has been helpful y'all.  Like I said, I'm not going to probably ever go hardcore DSO AP, just want something for light work eventually.  Yes I can eventually grab something else if I so choose, who knows...the technology might improve in the next 5 years.

Anyway, I think I am going to go for the 8" Edge HD AVX.  That seems to be a nice sweet spot for a lot of things.  Can someone tell me if this set-up would work or if there are things you would include/exclude?

  • Advanced VX 8" EdgeHD Telescope
  • DEW SHIELD DX FOR C6 & C8

  • STARSENSE AUTOALIGN

  • NEUTRAL DENSITY MOON FILTER - 1.25"

  • 8-24MM ZOOM EYEPIECE - 1.25"

I might add in the reducer and possibly a better finder. But looks like my buying list! 

 

52 minutes ago, Maideneer said:

I think I'm gonna wait on a reducer because I'll think about getting a Hyperstar which I am reading does a fantastic job and I also have to think about a proper camera.  Right now I'm going to solely focus (ha) on visuals for a while so I can get familiar and acclimated to everything.

Sounds sensible. Will be very interested to hear how you get on.

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Amazing!  I just pulled the trigger and made my purchases!  Had to go to three different sites to find everything in stock and then price compare, but here is what I ended up with.

  • Advanced VX 8" EdgeHD Telescope
  • DEW SHIELD DX
  • STARSENSE AUTOALIGN
  • SkyPortal WiFi Module
  • NEUTRAL DENSITY MOON FILTER
  • EclipSmart White-Light Solar Filter
  • 8-24MM ZOOM EYEPIECE
  • X-Cel LX 5 mm Eyepiece
  • Smartphone Adapter DX Kit

I think that will basically set me up for visuals for a good long time lol.  AP can come later, but I basically just spent 3 grand as a treat to myself for surviving these past few years - getting through a long bout of depression and anxiety, finding a new job and coming out the other end much happier.

Thank you everyone for awesome advice, I think I'm going to be busy very, very soon.

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Posted (edited)

Oh, that sounds really nice and I am sure you will be happy with your new instrument! The best of luck to you and if you get into imaging that is a really good scope for it. Just have a look at Astrobin and search for EdgeHD8.

We are finally seeing the light at the end of the tunnel. I had my first covid shot today!

Edited by gorann
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