Which one should I buy?

[mystyco]

Hi guys,

 

I'm using a Celestron 130 SLT Alt-Az mount, and I want to upgrade to something with a better tracking. I'm down to two options:

 

- Refractor (80mm ED) + ioptron mini tower v2

- Celestron Evolution 6''

 

Which one of the above would be a better choice for video astronomy? In terms of precise tracking, and resolution?

 

Thanks so much in advance for your help!

[DoctorD]

Hi

I had a Minitower V2 for a year and swapped it for a HEQ5 - the Minitower was great when it worked, however I had problems with alignment and goto accuracy that finally made me want to get rid of it (especially when loaded up with my C8).

Paul81 runs a Minitower V2 - perhaps he can give a more positive view of this.

The Celestron EVO 6" looks like a nice scope/mount but you'll need a focal reducer for EAA - Hyperstar would work if you can stretch that far, alternatively the F3.3 reducers should work if you can find one or a 1.25" x0.5 or x0.6 would also work - you should aim for F5 or below - I work at about F3.5.

I'd be inclined to go for the Celestron as it also has NextRemote for remote control which can be useful as it's usual to operate the scope & mount remotely in EAA (that's part of the attraction - staying inside nice and warm).

Alternatively you could always consider the ubiquitous HEQ5 Pro and EQMOD or Synscan and the scope of your choice - keep it at or below F5 and you'll be good for EAA with todays cameras such as the Lodestar X2.

You should also check out the potential field of view with each scope/camera/reducer option - the cameras used for EAA are relativley small chips with small FoV - I have a range of scopes to give different field of view:

C8 with F3.3 reducer and Lodestar-C - 0.52x0.41 degrees

MAK102 with F3.3 reducer and Lodestar-C - 0.71x0.55 degrees

INED70 with AE x0.6 reduced and Lodestar-C -  1.78x1.37 degrees

Check out my gallery to see how this relates to various objects or use Stellarium to simulate the views.

 

 

 

HTH

Paul

 

[Astrojedi]

I would recommend the Evolution. I use a Evolution 8 for EAA. It is an excellent mount almost tailor made for EAA. Very accurate gotos (I use Starsense) and accurate tracking up to 60s using the C8 and 90s using my AT72ED. I think you will need some kind of PEC for exposures longer than that.

 

[HiloDon]

My vote is for the Evo 6.  The SkyPortal wifi eliminates an extra wire and hand controller if you want.  Celestron has a free app based on the SkySafari app, but the cheap one with limited object catalogue.  SakSafari Pro 4 will work, but you need the latest update.  The tracking is much better than the 6se that I returned because of a handset malfunction.  I don't use StarSense, but the go to's are spot on.  The SE was, too.  I align with the camera in the focus mode and get the star right in th center of the crosshairs.  I also end with the up and right alignment buttons.

You can get Hyperstar for it and get some great wider field shots.  I think you have seen some of mine with the SE.  You could also get a short focal length refractor and run it on the Evo mount.  

Don

[mystyco]

35 minutes ago, HiloDon said:

My vote is for the Evo 6.  The SkyPortal wifi eliminates an extra wire and hand controller if you want.  Celestron has a free app based on the SkySafari app, but the cheap one with limited object catalogue.  SakSafari Pro 4 will work, but you need the latest update.  The tracking is much better than the 6se that I returned because of a handset malfunction.  I don't use StarSense, but the go to's are spot on.  The SE was, too.  I align with the camera in the focus mode and get the star right in th center of the crosshairs.  I also end with the up and right alignment buttons.

You can get Hyperstar for it and get some great wider field shots.  I think you have seen some of mine with the SE.  You could also get a short focal length refractor and run it on the Evo mount.  

Don

Hi Don,

Your images are very inspiring and truly amazing. I love galaxies and nebulae. For these objects should I get the 6'' SCT? Or a 80mm ED refractor on the evolution (or my current SLT mount) ?

Thanks in advance.

[HiloDon]

18 minutes ago, mystyco said:

Hi Don,

Your images are very inspiring and truly amazing. I love galaxies and nebulae. For these objects should I get the 6'' SCT? Or a 80mm ED refractor on the evolution (or my current SLT mount) ?

Thanks in advance.

Thanks.  I would say that the 6" SCT with focal reduction of .5 to .8 will give you a better focal length for galaxies with the exception of M31.  Planetary nebulae would be best at the native 1500mm FL.  Other Nebulae will vary and wider FOV optics would be necessary.  There the 80mm refractor with focal reduction would work well.  Hyperstar would be needed for the C6 to get the wide FOV nebulae like the Rosette.

Don

[mystyco]

11 minutes ago, HiloDon said:

Thanks.  I would say that the 6" SCT with focal reduction of .5 to .8 will give you a better focal length for galaxies with the exception of M31.  Planetary nebulae would be best at the native 1500mm FL.  Other Nebulae will vary and wider FOV optics would be necessary.  There the 80mm refractor with focal reduction would work well.  Hyperstar would be needed for the C6 to get the wide FOV nebulae like the Rosette.

Don

Hi Don,

I apologize for the ignorant question, but which would be faster, a 0.5 reducer or a 0.8? What f/ratio I would get with the Evo6 and these reducers? I also assume they are quite expensive?

thanks so much once again for your support!

[HiloDon]

24 minutes ago, mystyco said:

Hi Don,

I apologize for the ignorant question, but which would be faster, a 0.5 reducer or a 0.8? What f/ratio I would get with the Evo6 and these reducers? I also assume they are quite expensive?

thanks so much once again for your support!

The .5 and .8 are actually multipliers of the native focal length and ratio.  So they are .5x and .8x, respectively.  The native C6 (without any reduction) has a focal length of 1500mm with a focal ratio of F10.  The faster setup would be with the .5x reducer making the focal length 750mm with a focal ratio of F5.  The .8x will give a focal length of 1200mm at F8.

There are a lot of threads about focal reducers.  Some inexpensive popular ones are a Celestron 6.3 and the GSO 1.25" .5x.  The 6.3 is a .63x reducer.  The spacing on the 6.3 can be reduced to give the .8x if you need it.  If you're using this with your Infinity, going less than .5 may give you some aberrations and vignetting. 

Don

[mystyco]

1 hour ago, HiloDon said:

The .5 and .8 are actually multipliers of the native focal length and ratio.  So they are .5x and .8x, respectively.  The native C6 (without any reduction) has a focal length of 1500mm with a focal ratio of F10.  The faster setup would be with the .5x reducer making the focal length 750mm with a focal ratio of F5.  The .8x will give a focal length of 1200mm at F8.

There are a lot of threads about focal reducers.  Some inexpensive popular ones are a Celestron 6.3 and the GSO 1.25" .5x.  The 6.3 is a .63x reducer.  The spacing on the 6.3 can be reduced to give the .8x if you need it.  If you're using this with your Infinity, going less than .5 may give you some aberrations and vignetting. 

Don

The famous Meade 3.3 (similar reducers also available from another brand) would  work as well correct? I think this type of reducer would be faster than f/5 If I'm not mistaken.

Thanks!

[HiloDon]

Yes, it's faster, but if you use it with the Atik Infinity, you will get coma in the corners and vignetting.  The most reduction this larger 825 sensor can handle is .45 to .5x.

Don

[aparker]

12 hours ago, mystyco said:

Hi Don,

Your images are very inspiring and truly amazing. I love galaxies and nebulae. For these objects should I get the 6'' SCT? Or a 80mm ED refractor on the evolution (or my current SLT mount) ?

Thanks in advance.

Even with the central obstruction, the 6" SCT has 3 times the light gathering of an 80mm frac, and with a Hyperstar can get you to a shorter FL than the frac for wider views.  I have not used the Evo myself but hear good things about it.  

[aparker]

4 hours ago, HiloDon said:

Yes, it's faster, but if you use it with the Atik Infinity, you will get coma in the corners and vignetting.  The most reduction this larger 825 sensor can handle is .45 to .5x.

Don

That may depend in part on the focal reducer.  The Optec NextGen 0.33x reducer has a claimed flat field of 11mm, which would work for the Lodestar and be very close for the Ultrastar.

[Dave In Vermont]

A good overview of focal-reducers, and their employ and set-up, can be found in this paper:

http://www.mallincam.net/uploads/2/6/9/1/26913006/focal_reduction_for_dummies.pdf

Though written around the MallinCam-line of video-cams - it's pretty much universal.

Hope it helps -

Dave

[HiloDon]

4 hours ago, aparker said:

That may depend in part on the focal reducer.  The Optec NextGen 0.33x reducer has a claimed flat field of 11mm, which would work for the Lodestar and be very close for the Ultrastar.

Alex,

I'm a bit skeptical of Optec's recent claim.  Their original specs claimed 9mm.  Now they say 11.  I have the newest Optec .33x reducer and here are two images taken with it at .33x and .45x.  The vignetting doesn't show well on these, but it's there on the F3.3 image.  The coma is obvious in the F3.3 image.

Don

[aparker]

6 hours ago, HiloDon said:

Alex,

I'm a bit skeptical of Optec's recent claim.  Their original specs claimed 9mm.  Now they say 11.  I have the newest Optec .33x reducer and here are two images taken with it at .33x and .45x.  The vignetting doesn't show well on these, but it's there on the F3.3 image.  The coma is obvious in the F3.3 image.

Don

Don,

I would agree - there's definitely visible coma in the corners of the 0.33 image.  Probably better run at 0.4x or more if you want a really nice flat field.  And, for most galaxy targets, since you've got the 8" light grasp, why not go to a longer FL and capture more detail?  Ultimately, even starting at f/10, 0.33x reduction makes a very steep light cone, so there's really only so much flat field you can expect, unless you want to pay really big $ for very sophisticated multi-element optical systems.  I'm thinking here about either Hyperstar lenses or the ASA 0.7x Newtonian coma corrector/reducer, which will supposedly take an f/4 Newt down to a well-corrected f2.8.  Both will run you close to $1000, i.e. for a 6-8" system, considerably more than the OTA itself.  

[mystyco]

I've decided to get a Evo 6'' hopefully it won't be much of a difference between the 6'' and 8'' (I really wanted 8'' but the prices in Europe are crazy).

Thank you so much everyone, for helping me with my decision. I've received a tremendous amount of great feedback, and knowledge. This is the beauty of astronomy. It brings us all close together. You are amazing.

[aparker]

15 hours ago, mystyco said:

I've decided to get a Evo 6'' hopefully it won't be much of a difference between the 6'' and 8'' (I really wanted 8'' but the prices in Europe are crazy).

Thank you so much everyone, for helping me with my decision. I've received a tremendous amount of great feedback, and knowledge. This is the beauty of astronomy. It brings us all close together. You are amazing.

I think you'll be very happy with the 6".  With a sensitive detector like a Lodestar or Ultrastar you will still be able to see more with that small and portable scope than you could see by eye through a 20" reflector.

[Astrojedi]

Great choice. I don't think the difference will be that great. Make sure you get a good sensitive CCD.

[mystyco]

My CCD is the Atik Infinity.

[aparker]

31 minutes ago, mystyco said:

My CCD is the Atik Infinity.

Does the Atik software allow pixel binning?  Just curious...

[Astrojedi]

It does but when you bin the color camera you lose color.