19 replies to this topic

[KrisJot]

Hi All,

 

I am looking for a telescope with bigger aperture for typical visual observations (also with UHC, OIII, H Beta filters) that would show me DS (also for double stars) brighter than the currently owned TS 115/805.
I initially thought of two options:
a). to use my MAK Orion 180 with 0.6x 2" FL reducer;

b). to purchase of Bresser AR-152S / 760 with Petzval corrector

My mount is a iOptron CEM 26.
 

 

Thanks in advance for any advice!

Edited by KrisJot, 29 January 2023 - 06:39 PM.

[macdonjh]

From your post it looks like you don't intend photography with your TS115 and simultaneously doing visual with your new scope?  The new scope would be mounted on whatever mount you currently use?  The 7" Maksutov is a nice scope.  I think the AR-152 would be too much scope for your mount.  The chromatic aberration might also make double stars difficult.  A 6" or 8" SCT is also compact, like the Maksutov and either would be light enough for your current mount to carry well.

[havasman]

A 115mm f7 refractor plus a medium sized (8 to 12") Newtonian telescope on a Dobsonian mount are a fine match that complement each other's strengths to make a very powerful observing kit. Teleskop-Express offers a wide range of good options to the European market - https://www.teleskop...Telescopes.html

 

Resolution and brightness will be considerably higher via the larger apertures.

Edited by havasman, 29 January 2023 - 07:22 PM.

[KrisJot]

From your post it looks like you don't intend photography with your TS115 and simultaneously doing visual with your new scope?  The new scope would be mounted on whatever mount you currently use?  The 7" Maksutov is a nice scope.  I think the AR-152 would be too much scope for your mount.  The chromatic aberration might also make double stars difficult.  A 6" or 8" SCT is also compact, like the Maksutov and either would be light enough for your current mount to carry well.

Thanks for reply, Yes TS115 will be used for AP mostly. AR152/760 is planned for visual only. About Mak 7", I've a 0.6x reducer for it. Will it be comparable on DS's (including double stars) to AR152/760?

[KrisJot]

A 115mm f7 refractor plus a medium sized (8 to 12") Newtonian telescope on a Dobsonian mount are a fine match that complement each other's strengths to make a very powerful observing kit. Teleskop-Express offers a wide range of good options to the European market - https://www.teleskop...Telescopes.html

 

Resolution and brightness will be considerably higher via the larger apertures.

Few days ego I've tested my first ATM Newton 223/2248mm with silver coating, but this "baby" is US dedicated one. DS is also possible, but no go-to and smaller FOV makes it more difficult on finding dimmer DS.

That's why I'm looking for something for visual applicable on CEM 26 with bigger aperture. That's why I thought about alternative option for AR152 as currently owned Mak 7" with FL 0.6x reducer.

Edited by KrisJot, 29 January 2023 - 08:35 PM.

[SeattleScott]

The CEM26 is GoTo so I would just use the Mak. Yeah it won’t do Pleiades but it will fit a lot of stuff and do double stars.

Double stars are interesting, they seem almost biased towards refractors in my limited experience. An achro might have an edge over the Mak on double stars, not sure. At least as long as the double isn’t too bright.

[drd715]

Limiting youself to the CEM-26 and for visual the AT-130EDT will collect enough light to provide a good visual view. Crip enough CA limited it should do a resonable job splitting doubles . To get more light and more resolution you will need more aperture - 8 inches in a reflector or more. At some point you are mount limited. Visual long focal lengths may become quite shaky on your mount.  

[KrisJot]

What about idea of using a focal 0.6x reducer with MAK 7"? Will it give comparable brightness on DS to AR152/760 (also with UHC & OIII filters)?

Edited by KrisJot, 29 January 2023 - 09:54 PM.

[Tony Flanders]

Thanks for reply, Yes TS115 will be used for AP mostly. AR152/760 is planned for visual only. About Mak 7", I've a 0.6x reducer for it. Will it be comparable on DS's (including double stars) to AR152/760?

Yes, a 7-inch Mak will do better than a 6-inch refractor on double stars, except in the rare case of a double with a faint secondary that happens to lie on the innermost diffraction ring of the brighter star. And the two scopes will be more or less comparable for deep-sky objects.

For truly superior views, of course, you need some real aperture, presumably a reflector. A 12-inch Dob would show deep-sky objects far better than any of the scopes you have mentioned.

[JOEinCO]

I have the f/5 760mm focal length Petzval Bresser AR152S.

 

While I agree with Tony that a larger scope such as a 12" Dob will outperform everything you list, the 6" Petzval scope does a very respectable job on all the dimmer deep space targets. Pleaides, no. Caroline's Rose, yes. On galaxies, nebula, globulars and distant open clusters (which is most open clusters), the views are quite comparable to 6" APOs. Even double stars will be quite good unless one of the stars is brighter than about magnitude 4.

 

The short-ish 760mm effective focal length gives amazing wide-field views. Sweeping the summer Milky Way is just plain fun. 3° true FOVs are fairly easy with eyepieces like the AT 28mm UWA or an ES82/30 or 35mm Panoptic, and 3.4° can be reached with some of the widest eyepieces (though you start getting into large, 8mm exit pupils with eyepieces like a 41mm Panoptic).

 

Keep in mind, though, that the 152mm Petzval is physically the same size as the regular AR152 - the rear Petzval lens just makes it optically shorter. And because it's AR152-sized with a second lens cell in the back, it's heavier than the regular AR152. So it's going to ask a lot of a mount as macdonjh mentioned.

[Paul Sweeney]

For visual, aperture rules. That goes for faint fuzzies and planets/moon. So get a good sized dob. My 12" dob blows my smaller scopes right out of the water.

[BrentKnight]

Of course it's your choice, but swapping OTA's on a single mount get's old for me.

 

Why are you not happy with DSO's with your 115?  I don't believe there will be that much difference for fainter DSO's going up to the 125 - 130mm range.  Open clusters, some nebulae (with filters), brighter galaxies should be visible in your existing refractor with only some improvement in the slightly larger refractors (and I think anything over 130 would be a challenge with the CEM26).

 

If you don't want a Dob, I'd recommend seeing what you can do with the Mak. 

[EsaT]

I am looking for a telescope with bigger aperture for typical visual observations (also with UHC, OIII, H Beta filters) that would show me DS (also for double stars) brighter than the currently owned TS 115/805.

I initially thought of two options:
a). to use my MAK Orion 180 with 0.6x 2" FL reducer;

b). to purchase of Bresser AR-152S / 760 with Petzval corrector

Maksutov is FOV "challenged" no matter what. It's limited also by physical design and not just focal length.

 

152mm aperture would increase light gathering ability by just 74%.

That isn't much for visual deep sky.

And for price of that Bresser you could get good 10" Dobsonian like GSO made Levenhuk.

Besides resolving power of big aperture it would collect 370% more light than that 115mm aperture.

https://www.astrosho...50n-dob/p,71266

While it lacks RACI finder of Apertura AD/Zhumell Z of sold in US and British FLO's StellaLyra, it still comes with dual speed focuser and decent actual wide angle instead of generic non wide 25mm Plossl.

[SeattleScott]

He has a 9” reflector, but it doesn’t have GoTo and the FOV is a bit narrower for finding DSO. So he has aperture available but he wants either GoTo, wide FOV or both. The mount is GoTo so I would suggest just using the Mak since wide AFOV isn’t that important when you have GoTo, and the iOptron mounts aren’t really that great for using just manual without GoTo anyway.

[macdonjh]

I'll stick with my assumption KrisJot wants to keep his gear collection small and not accumulate a mount for each scope.  If that's the case, then I think the 7" Maksutov is the most practical choice of the two scopes being considered.  The 0.6x reducer gets the focal length down to 1600mm or so.  Still not a widefield instrument, but sort of comparable to an 8" SCT, which can show a lot of deep sky objects.  Remove the focal reducer and high magnification can be had with medium-to-long focal length eye pieces for splitting double stars.  

 

I mostly agree with what BrentKnight posted, but will say when I jumped from a 4" Maksutov (my family's first scope) to a 6" achromat I was shocked by how much brighter objects I was familiar with appeared and how many more objects I could see.  So the jump from 115mm to 130mm might not be much, but the jump to 152mm (or 180mm) is substantial in my experience.  That said, the jump to 250mm or 300mm would be mind blowing.  I'd have recommended a Dobsonian as well, if he hadn't originally posted he wanted to use his existing mount with his new scope.  He also may not be able to store a scope that big, or willing to move it to his observing spot and back (small doors? stairs?).

[KrisJot]

Thank you for your valuable remarks.
Today, hunting for holes in the clouds, I managed to get better to know the AR152. it is indeed a very nice refractor. On the moon, it withstood 250-270x magnification. The stars are also nicely shown pointwise. There is aberration, but it didn't bother me at all. After thinking about it for a long time, I decided to not buy this telescope. As you suggested, it did not bring a new quality to the currently owned ones.

For now I'm thinking of using the APO115 for widefield DS and test the Mak with the reducer and use it for more compact ones, which requires higher magnification (including double stars). I also have a ATM planetary newton 9.5" to check. The first observations were promising despite average atmospheric conditions, but it is not enough to assess its capabilities. Ultimately, I plan to equip it with electronics supporting the search for objects in the sky, unless I learn the night sky by then. As for the larger mirror typically on the DS, I started building a 16" F 4/5, but this is a another one year project :-).

[BrentKnight]

I think that sounds like a pretty good plan...

[GSBass]

Ed ting talks about the mak in his latest review of an intes version….feel like most of what he said fits generically and is true, a 7” is definitely worthy of being in your collection for planetary, lunar and doubles, I have the old Orion version and love it

[KrisJot]

I tested my 7" Orion Mak with one the old 1.25" focal reducer but it makes some vignetting in visual (only). I found some inexpensive focal reducers from GSO 2" 0.5x (~50mm back-focus) and GSO 0.75x for RC. Did You have same experience using them with MAK?

Edited by KrisJot, 19 February 2023 - 07:31 PM.

[EsaT]

I tested my 7" Orion Mak with one the old 1.25" focal reducer but it makes some vignetting in visual (only). I found some inexpensive focal reducers from GSO 2" 0.5x (~50mm back-focus) and GSO 0.75x for RC. Did You have same experience using them with MAK?

It's physical design of Maksutov which sets limit for FOV, not just long focal length and high magnification.

Focal reducers can't fix that.

Unlike Barlows(/focal extenders) helping with short focal length and low magnification.

That's the price of design giving that long focal length in compact size.