800mm focal length refractor

[Merlin66 (Ken)]

Can any one recommend a suitable refractor for solar work.
Needs a focal length around 800 - 850mm

[Merlin66 (Ken)]

Hmmmm
No suggestions, no recommendations???

[MortonH]

Does it need to be ED/apo? Is 900mm too long? (thinking ED100 f/9)

[Merlin66 (Ken)]

Just needs to be a good achromatic.....
900mm focal length would be too long, say 850mm max.

[rustigsmed (Russell)]

hmmm there really aren't many refractors around 800-850mm!

[bojan]

Try one of Rubinars.. after glass relaxation, my Macro 10/1000 is diffraction limited.
Ops.. I had a look at ebay, prices went up 5-fold from times I bought mine (from rugift.com)


I also have this one.. not bad as a visual telescope, not too many CA.
When Sun is up, atmospheric turbulence will be a dominant problem anyway.

[Merlin66 (Ken)]

Bojan,
Looks much longer focal length than what I need.
850mm is around the max.

[bojan]

Opteka (MZ-5000) has adjustable FL, 650-1300 mm.

Rubinars 8/500 would be good.. sometimes they appear on ebay for less.

[Eldest_Sibling (Alan)]

It has a dovetail-bar, for placement onto other mounts, but no tube-rings, and rings for this one would be virtually impossible to find online...

EDIT: http://www.saxonoptics.com/products/...roductid=10011

...however pipe-clamps served for this "de-forked" 50/600, at f/12...



...a bit of DIY.

Only a safe solar-filter can be attached, at front over the aperture; no Herschel wedge or other, as the telescope is plasticky. Achromatic refractors from 40mm to 76mm were once of all-metal, the focusser and the doublet's lens-cell in particular.

[Merlin66 (Ken)]

Alan,
Thanks, but I think the costs to ship from the US to Australia would far exceed what the scope is worth.

[MortonH]

Ken,

Probably a silly question but does the scope need a native focal length of 800mm or could you use a shorter/longer one with some kind of focal extender/reducer?

[Eldest_Sibling (Alan)]

Originally Posted by Merlin66

Alan,
Thanks, but I think the costs to ship from the US to Australia would far exceed what the scope is worth.

I've edited my post, and with the Saxon equivalent.

[Merlin66 (Ken)]

Morton,
Not a silly question.
Using a Barlow, they have limited backfocus spacing which can put the optics close to the prime focus. Not a good situation when working without filters Solar imaging with larger apertures.
I’m looking at the x0.75 GSO reducer (to use with a 1000mm refractor) - it has a working back focus of 80mm .

[Eldest_Sibling (Alan)]

If the Saxon 608 seems viable, I cannot find the model among the three vendors I searched. It may be discontinued, or available as a special order.

Oh, I almost forgot: my own 4" refractor has an 820mm focal-length.

[Nikolas (Nik)]

Bresser makes some of that scale
also nat geo?
I know they are cheap but they are an achro of that focal length


Or something like this? it's 714mm or is that too short?

[anj026]

Hi Ken,

I see that the Scopetech 80mm lens are now available from FLO.
The 80mm f10 lens works out to approx $210 AUD inc postage.

https://www.firstlightoptics.com/sco...-and-cell.html

Andy

[Merlin66 (Ken)]

Andy,
Appreciate, but I need a bit more aperture.
A 120mm with a focal length of 900mm (not necessarily an ED version) would be ideal.

[anj026]

How about the Explore Scientific AR 127 f6.5, 826mm focal length?

http://www.frontieroptics.com.au/Exp...t%20Series.htm

Andy

[Merlin66 (Ken)]

Looks good what about price?

[Tropo-Bob (Bob)]

Occasionally, there is Vixen 140mm SS in the classifieds. Its focal length is exactly 800mm. The going price seems to be a little over a $1,000 ($1200 to $1,400).