66mm or 71mm Apo Refractor for imaging ???????

[mystarrymessengr]

Hi all 

seeking some expert advice from owners of short tube refractors of 66mm or 71mm. I'm looking at investing in a short tube Apo refractors for mostly imaging wide field scenes. But  before I take the plunge I keep being swayed back and forth between these two apertures. I would like to be able to look through my new scope so therefore would still like an impressive sight rather than just imaging through it. So my question is two fold really. 

1. What would the difference in image size through the eyepiece from a 71mm to 66mm given a similar focial length

2. Visually what would the difference be for the above aperatures 

3. Would imagers on here be kind enough to share any images captured through either of the above. 

 

Just for the record the two scopes I'm looking at are 

- William optics zenith star 71

- Altair Astro 66 

 

Thanks in advance 

clear skies as always 

[Moonshane]

Whilst both would provide very similar visual views, and decent enough for their aperture, I personally was never satisfied with aperture under 100mm for visual.

[mystarrymessengr]

Thanks for your comment 

[RayD]

Any reason why specifically these apertures?  If you are looking to use for visual also there are a lot of very good 80mm APO's out there which may offer a little better visual use, but also a generous FOV for imaging.  After all if you really want wide field you could always do a mosaic?

[mystarrymessengr]

Hi. Ray D. Yeah I'm looking at downsizing my rig for a more kportable travel package. I already own a 80mm ED on a HEQ5. But I'm looking for a small wide field fast travel style scope which I will be mounting on a tracking system, so weight is a big issue hence looking at the 66mm or the 71mm. I've heard good things about both but I wondered if anyone who owns these scopes wouldn't mind sharing their work on here? 

[RayD]

2 minutes ago, mystarrymessengr said:

Hi. Ray D. Yeah I'm looking at downsizing my rig for a more kportable travel package. I already own a 80mm ED on a HEQ5. But I'm looking for a small wide field fast travel style scope which I will be mounting on a tracking system, so weight is a big issue hence looking at the 66mm or the 71mm. I've heard good things about both but I wondered if anyone who owns these scopes wouldn't mind sharing their work on here? 

Ah ok makes sense.  There are a fair number of star71 images I've seen on here and they are very good indeed, and they do seem pretty popular, so without searching hopefully someone will be able to share theirs with you.

[ronin]

The WO ZS is a doublet and a little fast so expect some CA to show through. So also it seems is the Altair 66 a doublet.

If same focal length the the images should be identical size, the difference being the ZS should produce a slightly brighter image. However likely nothing in it that would make a great amount of difference.

I see Altair do a 70mm triplet, that should eliminate CA but it costs £600 and that is a fair jump from the £370 for the 66mm. More then I would jump to.

I would go for the 71, mainly as it would make a nice visual scope when youi are not imaging. WO's are nice but they also cost more. So you could easily be back in the realm of the cost of the Altair 70mm triplet.

[Macavity]

Not an easy one! Recently "Been there, Done that" re. this very choice. 

Eventually bought an Altair ED66-R. So far I have had insufficient use to
for any detailed opinions! But e.g. I was quickly disavowed of the idea it
would sit atop my main scopes on an HEQ5. (APOs are quite "chunky!) 

I guess one can read Equinox 66 reviews re. performance of the scope!
FLP51/53 glass etc. Who knows? The Altair Astro is beautifully made and
"looks more like a scope" [IMO] than Skywatcher Equinoxes? [teasing] 

At f/400mm (I discover) just fails to fit the lunar/solar image on a 1/3"
chip (ZWO 120MM) etc. So had to invest in a pukka 1/2" chip now Doh!
My aim is to bridge the IMAGING gap between my longest telephoto
lens (200mm) and my other telescopes... That, I think it will do well!  

Visually? If one's only experience was with fast achromats (an ST102)
one will be impressed with a first true APO (OK, semi-APO!) -- Blown
away by the lack of colour etc. Kind of wish I'd gone for an ED80-R? 
But that would be more of a "main scope" re. (limited) portability...

To test out true visual limits, I will have to re-buy some eyepieces! 

[mystarrymessengr]

Thanks all for your advice and input so far. Would still love to see some images taken through either of these scopes 

[hi8ane]

As a relative newcomer I can't comment with much depth of knowledge or experience but I came into this hobby by purchasing the Altair Astro ED 72R with the iOptron EQ Pro mount and the Altair Astro mono GPCAM and a 15mm eyepiece so can only comment on this setup.

It is certainly portable although not as simple as it sounds as you have the carry case containing the scope, EP, controller, diagonal and camera. In addition you need to carry the mount with its counterweight which is awkward but not too heavy. Then the tripod which collapses to a modest size. After some practice I can now setup from scratch (everything packed away in an upstairs room) to imaging in the back garden in less than ten minutes and pack away in the same.

I've been delighted with the setup both for visual and imaging use but have learnt that there are plenty of "gotcha"s during the learning phase. The main one being the field of view which is either too large or too small but you learn to live with that by buying more stuff.

Visually the view of stars is excellent with pin sharp stars on a jet black background. I've not been disturbed by any distortion and see no colour aberration. In fact double stars are often further apart than Stellarium or Sky Safari would suggest. Something like Albireo is a wonderous sight yet the Pleiades are disappointing as the bright fuzzy blob turns into a mass of sharp points of light.

The attached images are my favourites so far. All except the waxing moon were taken using a x3 Barlow which pushes the limits of the scope.

 

[mystarrymessengr]

Fantastic these are brilliant images , you should be really proud 

 

thank you for sharing them