SCT, Mak or frac?

[Sunshine]

6 minutes ago, johninderby said:

Yup and fits nicely into my scope lineup.  Hope the OP finds a scope that will suit them but there are so many nice scopes out there now can be a confusing choice.

True, but how many of those are available within a donkeys age? its a sad state the market is in.

[OK Apricot]

Incredible how high the prices have risen. With a refractor I'd be looking for an EQ5 minimum, which isn't too bad but then to have the luxury of Go-to and maybe a bit more future proofing for imaging, the HEQ5 - that takes this package up to a good 4 figures.

From another perspective, the Skymax 127 Mak is just shy of £600, looks nice and manageable and has go-to. With the price in mind, does it sound like a decent compromise? After all, that's what this hobby is all about! 

[johninderby]

The Skymax127 AZ-GTi is very popular and just over £500.00. The AZ-GTi mount is pretty good and can be used in EQ mode with the addition of a wedge.

https://www.firstlightoptics.com/telescopes-in-stock/sky-watcher-skymax-127-az-gti.html

[michael.h.f.wilkinson]

A C8 is very grab and go especially if stored in a cool garage so you don't have cool-down time. It outstrips the performance of my excellent little APM 80mm triplet on planets.

[dweller25]

22 minutes ago, OK Apricot said:

Incredible how high the prices have risen. With a refractor I'd be looking for an EQ5 minimum, which isn't too bad but then to have the luxury of Go-to and maybe a bit more future proofing for imaging, the HEQ5 - that takes this package up to a good 4 figures.

From another perspective, the Skymax 127 Mak is just shy of £600, looks nice and manageable and has go-to. With the price in mind, does it sound like a decent compromise? After all, that's what this hobby is all about! 

Just to put things into perspective…..

The Skymax 127 just shy of £600 you mention is manageable but the eyepiece views will be beaten in all areas by your Skywatcher 200P 

[nfotis]

Another option is to buy used. I started in this hobby with a Skymax 127 and a beaten up HEQ5 mount myself, which were relatively easy to find even in Athens (which isn't exactly a hotbed of astronomy). If I remember correctly, I paid about 250 EUR for the Skymax (and various stuff), plus 550 EUR more for the HEQ5.

N.F.

 

[OK Apricot]

Thanks for the input, loads to think about and dribble over. Much appreciated. 

[Louis D]

15 hours ago, michael.h.f.wilkinson said:

A C8 is very grab and go especially if stored in a cool garage so you don't have cool-down time. It outstrips the performance of my excellent little APM 80mm triplet on planets.

Why is it that SCT planetary images look good, but every time I look at planets visually through SCTs at star parties, the views are always upstaged by nearby Newts with custom mirrors of similar aperture?  The only time an SCT gave comparable visual planetary views for me was through an 8" EdgeHD.  It was just as sharp as the views through the Dobs with custom mirrors.

[JeremyS]

2 hours ago, Louis D said:

Why is it that SCT planetary images look good, but every time I look at planets visually through SCTs at star parties, the views are always upstaged by nearby Newts with custom mirrors of similar aperture?  The only time an SCT gave comparable visual planetary views for me was through an 8" EdgeHD.  It was just as sharp as the views through the Dobs with custom mirrors.

Collimation? 
Some imagers go to obsessive lengths

[HollyHound]

20 hours ago, johninderby said:

I’ve found the CC6” holds collimation as well as a mak. Never had to touch the collimation since I got it.

I (briefly) had this very scope from @johninderby before selling it back and I can confirm, the collimation was spot on when it was delivered and (I presume) the same when returned... excellent scope and the only reason I let it go back was because I got a Mewlon 180 (another superb scope) 👍

[HollyHound]

On 14/02/2022 at 09:39, Nik271 said:

PS. To throw a spanner in the works a cheaper option is the 127Mak (SW or Bresser) , of course smaller aperture than the 6 inch CC but really light (3kg) and excellent up to x200 again. Cons: no widefiled, some dewing issues. Costs only about £350 or so.

Agreed... my second scope was a Mak127 and I still use it now, although admittedly less often (I just can't bear to sell it because it's so sharp and compact).... perfect for lunar and doubles 👍

[johninderby]

32 minutes ago, HollyHound said:

I (briefly) had this very scope from @johninderby before selling it back and I can confirm, the collimation was spot on when it was delivered and (I presume) the same when returned... excellent scope and the only reason I let it go back was because I got a Mewlon 180 (another superb scope) 👍

Yes collimation is still perfect. 👍🏻

Would be intesting to compare the Mewlon 180 with the Tecnosky 125. 🤔

Edited February 15, 2022 by johninderby

[HollyHound]

44 minutes ago, johninderby said:

Yes collimation is still perfect. 👍🏻

Would be intesting to compare the Mewlon 180 with the Tecnosky 125. 🤔

Yes indeed.... I have been contemplating getting a 5" class refractor for a while now, but between the FC-100DZ and Mewlon 180, I feel I have all bases covered currently... nice though it would be, I'm not sure whether it would add anything 🤔

For sure, the 5" refractor would give (slightly) better resolution than the DZ, but then it could never compete with the Mewlon on DSOs, and when cooled properly (which does realistically take over an hour) the Mewlon is superb on lunar 😀

I haven't ruled out the bigger refractor, just being cautious (yes, you read that right 🤣)about adding another scope into the mix right now for no real reason, especially as I'm really enjoying those that I have 👍

Edited February 15, 2022 by HollyHound

[michael.h.f.wilkinson]

3 hours ago, Louis D said:

Why is it that SCT planetary images look good, but every time I look at planets visually through SCTs at star parties, the views are always upstaged by nearby Newts with custom mirrors of similar aperture?  The only time an SCT gave comparable visual planetary views for me was through an 8" EdgeHD.  It was just as sharp as the views through the Dobs with custom mirrors.

Partly secondary obstruction, which is almost always smaller in a Newton. My old 6"F/8 with a very small secondary and 1/10th lambda mirror was a real planet killer. Not so much grab and go. The figure of the mirror makes a big difference too. The EdgeHD may have the better mirror than a run of the mill C8. When imaging you can boost contrast, of course, which negates much of the effect of a larger secondary. I would love to have (space for) an 8"F/8 Newton, it would almost certainly beat my SCT, but it would definitely not be grab and go

 

[cloudsweeper]

I've always thought my 8SE SCT was less sharp ("softer") than the Dob (and fracs of course).  It is well collimated, I believe.  I had contemplated eventually going for an Edge HD, but don't they have essentially the same optics as the basic SCT, except for a field flattener for AP purposes?  If so, I guess there would be no advantage for a visual-only person like me.

I look forward to comments on this!

Doug.

 

[johninderby]

As much as I love my CC8” can’t help wonder what the CC10” would be like. 🤔 

[Louis D]

16 minutes ago, cloudsweeper said:

I've always thought my 8SE SCT was less sharp ("softer") than the Dob (and fracs of course).  It is well collimated, I believe.  I had contemplated eventually going for an Edge HD, but don't they have essentially the same optics as the basic SCT, except for a field flattener for AP purposes?  If so, I guess there would be no advantage for a visual-only person like me.

I look forward to comments on this!

Doug.

 

Read this Celestron whitepaper on the EdgeHD.  Even in the center, the spot sizes are tighter than a typical SCT:

It might also be possible to get similar results with a Starizona flattener/corrector:

My point is, even on axis, SCTs need some optical corrector help at the rear baffle tube/port.

[cloudsweeper]

Thanks, @Louis D - the paper and chart indicate that an Edge HD would indeed be better for visual than the basic SCT, and that is what I want in order to get tighter splits more clearly.

When you say:          "My point is, even on axis, SCTs need some optical corrector help at the rear baffle tube/port."        - do you mean a corrector for the basic SCT would improve the sharpness, or that such a corrector is built in to the Edge series?

Doug.

 

[Louis D]

1 minute ago, cloudsweeper said:

Thanks, @Louis D - the paper and chart indicate that an Edge HD would indeed be better for visual than the basic SCT, and that is what I want in order to get tighter splits more clearly.

When you say:          "My point is, even on axis, SCTs need some optical corrector help at the rear baffle tube/port."        - do you mean a corrector for the basic SCT would improve the sharpness, or that such a corrector is built in to the Edge series?

Doug.

 

Both

[cloudsweeper]

12 minutes ago, Louis D said:

Both

What would this be as an add-on for the basic 8SE?  I'd really like something to improve its sharpness without spending a fortune on an Edge HD model.  

Aperture (8" or more),  GoTo, and sharpness would be a great combination!

Doug.

[Louis D]

16 minutes ago, cloudsweeper said:

What would this be as an add-on for the basic 8SE?  I'd really like something to improve its sharpness without spending a fortune on an Edge HD model.  

Aperture (8" or more),  GoTo, and sharpness would be a great combination!

Doug.

I'd probably start with a Celestron 0.63x reducer/corrector if you already have the 8SE.  I can't find an SCT corrector that isn't also a focal reducer.  However, these don't play well with short focal length eyepieces.  From what I've read over the years, you don't want the R/C present at high powers.  I see something similar with the GSO CC in my Dob and the TSFLAT2 in my fracs.  Both contribute spherical aberrations at high powers that overshadow any intended correction.

The Starizona R/C is much more expensive, but probably achieves better correction.  I'm not sure how applicable it would be to visual work, though.

The difficulty of trying to get absolute sharpness with SCTs is probably why other designs are more popular for high power visual work.

[OK Apricot]

One of the better thread hijacks - some good reading and diagrams especially 👍

[Louis D]

On 13/02/2022 at 11:53, OK Apricot said:

My mind has been wandering today, thinking how I've got my light bucket, now I need something laser sharp for the solar system.

Have the primary refigured to 1/10th wave or better if it isn't already, decrease the size of the secondary to no more than 20% obstruction by diameter, and replace the focuser with a low profile focuser.  My best planetary views have been through 8" to 12", well collimated Dobs with custom mirrors like Zambuto and an undersized secondary.  The low profile focuser gets the eyepiece closer to the secondary to grab as much of the reduced cone of light as possible.  Of course, it might be cheaper to just start over and look for a used custom made Dob with full goto.

[JeremyS]

2 hours ago, johninderby said:

As much as I love my CC8” can’t help wonder what the CC10” would be like. 🤔 

2-inches bigger 😊

[johninderby]

27 minutes ago, Louis D said:

 

The difficulty of trying to get absolute sharpness with SCTs is probably why other designs are more popular for high power visual work.

And that’s the reason I went from the C8 to the CC8” . So sharp on axis.