ED80 vs. 4.7" refractor for visual?

[pluton]

Hello,
At this point, only for visual solar observation which is the best ?, ED80 refractor, or 4.7 "achromatic, the latter I have seen a model 120 F / 5 with a very affordable size for azimuth mount, and also 4.7 "F / 8.3 Celestron Omni, which already seems to me a bit long for azimuth mount ..

I've heard that a 4.7 "lens has a very good resolution solar observation (and others too) and it does not matter much that is achromatic.
A greeting and thanks
Paul

[Moonshane]

I can only comment on 80mm f11 frac vs 102mm f10 frac so not quite what you are comparing but here goes.

My (Vixen) 80mm frac gives more stable images in terms of seeing than my 102mm (Celestron OMNI) frac but in all honesty there is not much difference between the two in terms of overall detail shown/seen.

Both give more stable and slightly sharper views than my 6" f11 dob with solar film but I put this down to the lunt system. it's a shame you cannot use Lunt wedges on dobs.

in your shoes and given the two scopes suggested, I think I'd get the 80mm ED. BUT that's me and I have other scopes to choose from where larger aperture is desirable. 

[nicoscy]

Speaking from personal experience with both apertures, solar observing with a Herschel Wedge, the 120 will blow your brains out. The aperture is a deciding factor and suddenly the sun becomes alive in a way that you will never get with 80mm. Stick a cheap binoviewer and resolution takes another jump with the 120mm.

However, you need to have a decent mount for the 120mm and it is of course heavier and bulkier than the 80mm, so it actually depends on you willingness to engage heavily in solar observing. For quick looks, the 80mm is a very sensible choice.

[Stu]

I would tend to be wary of the faster achromats eg f5, but would think an f8 ish should be pretty good.

Assuming you use a continuum filter which is narrowband, the CA should not be an issue, image sharpness would just depend upon the fundamental quality and figuring of the lens.

Nicosy is totally right about mounting requirements too, the 120 needs a much beefier mount/tripod so is not what I would call grab and go. My 85 will still fill that role

Sent from my iPhone using Tapatalk

[nicoscy]

I used a 2" Baader Hershel Wedge and it comes with integrated Solar Continuum filter, hence a narrowband image with exceedingly good contrast and details.

If you plug an ERF filter, a UV/IR filter and a Quark in your scope, you are still doing narrowband in Ha so again it shouldn't be a problem.

[pluton]

             So, for example:
For a 120/600 refractor with Quark ep. would require an ERF in the objective lens, or it would also be a UV / IF filter before the diagonal?
Thank you

[nicoscy]

120mm is the limit where both filters are required according to literature.

[Stu]

Yes, I'm assuming I can just use a UV/IR cut filter at 120mm. Any bigger and a D-ERF would be needed although I have seen that up to 130mm is ok.

Alway check with your supplier first though, don't take my word for it!!

Sent from my iPhone using Tapatalk

[nicoscy]

I would still use the ERF even though up to 120mm the UV/IR is stated as sufficient. Better safe than sorry.....

[Stu]

This seems quite a confusing and ill defined area of the spec, and one which I think Daystar should clarify.

I have been communicating with Astrograf, and had good information from them, but they say there is no official recommendation from Daystar. SCS lists over 85mm as needing a UV/IR cut, and over 130mm as needing a D-ERF.

Sent from my iPhone using Tapatalk

[nicoscy]

This seems quite a confusing and ill defined area of the spec, and one which I think Daystar should clarify.

I have been communicating with Astrograf, and had good information from them, but they say there is no official recommendation from Daystar. SCS lists over 85mm as needing a UV/IR cut, and over 130mm as needing a D-ERF.

Sent from my iPhone using Tapatalk

Can't remember which vendor had 120mm on their site as the limit but you are absolutely right that Daystar should clarify. Solar viewing is inherently dangerous and clear cut instructions are essential.

[pluton]

Thank you for your response!

Then,                      

down  85mm is not needing a UV/IR cut, ?  exclusively for clarify!!

regards

Paul

[Stu]

I would not like to give you advice on this myself as I think it should come from the manufacturer.

Personally I will always use a UV/IR filter whichever size of scope even below 85mm, just to be sure.

Sent from my iPhone using Tapatalk

[pluton]

OK!

Thanks

Paul