Astrosolar filter on Maksutov 102

[Quaxo76]

Hello,

I have a question that's probably quite silly, but I can't figure this out.

I'm using a Skywatcher Mak 102, that's been performing really good. I mostly use it with a 7-21 zoom Svbony eyepiece. Everything looks mostly how I think it's supposed to look - moon, planets, a few nebulae and star clusters. The moon is perfectly detailed, I see the cloud bands on Jupiter, the shadow on the rings from Saturn's body, and so on. Visual only for now.

I wanted to observe the Sun too, and so I bought, on Amazon, a filter with the AstroSolar film, here's the link to the specific filter: https://www.amazon.it/dp/B098BBT7HP?psc=1&ref=ppx_yo2ov_dt_b_product_details
 

Looking at the Sun through the filter with the naked eye, there's no visible damage (i.e. no holes) and the Sun looks like a nice circle, though in places the image gets slightly distorted, as if there were small "crease marks".

But when I mount it on the telescope (it fits perfectly btw) the resulting image is awful. It's sort of as if the image was "smudged" in one direction. I mean, if I look at the Sun disc at low magnification, so I can see it whole, then there will be two opposite points in the Sun's border (i.e. up and down, or left and right, and so on) that are sharp, while the rest gets progressively more smudged, up to the place 90 degrees from the sharp point, and then it reverses until it's sharp again after 180 degrees. It's not easy to explain, but it's just as if the whole image got "smudged" in a single direction. There is no discernible detail at all on the Sun, no spots or anything, even though online services show several spots there right now.
If I rotate the filter around, then the sharp points in the Sun's disc rotate as well, which indicates that it's something to do with the filter (also the fact that the scope works perfectly otherwise).

The strange thing is that I lent the filter to a friend, who has different scopes (not Maksutovs), and he says the filter works for him, albeit not with great quality.

So I'm wondering, is there some incompatibility between these filters and Maksutovs? Maybe the filter sits too close to the front corrector plate? I tried concocting an extension, so that the filter sits a bit farther from the telescope, but (other than being super ugly and unbalanced) it doesn't improve the situation discernibly.

So what should I do if I want to observe the Sun spots without spending a fortune? Find a different AstroSolar filter, or change technology altogether? Should I just send the filter back and try again with a different model?

Thank you in advance,
Cristian

[wulfrun]

Since no-one else has answered...I don't see any reason why a Mak would be "incompatible" with a solar filter. If you're getting good views of the moon etc and not of the sun with the filter, logically the filter is defective in some way. I have no experience of that filter to guess how though!

You can buy solar film in A4 sheets and make your own. The sheets come with detailed instructions on how to make your filter and it's probably about the cheapest option. With a bit of care, it'll be just as good as a ready-made one, if not quite as neat.

https://www.firstlightoptics.com/solar-filters/baader-astrosolar-safety-film-nd-50.html

Or

https://www.firstlightoptics.com/solar-filters/explore-scientific-solarix-a4-solar-filter-film.html

Edited March 23 by wulfrun
links added

[Nik271]

I have used my Mak 127 with Baader's solar film for a long time with no issues. There is nothing in the design of the Mak that stops using front mounted solar filters. But note that backend filters like solar wedges are not compatible with the Mak design as the heat will build up inside it.

My advice is to reuse the purchased mounting cell but replace the solar film with Baaders one.

Edited March 23 by Nik271

[Quaxo76]

Thank you for your replies. I was planning on sending it back, but since the mount fits my scope perfectly, you're right that it might make sense to replace the active part of the filter.

I'll keep the filter then (let's say I bought a rather expensive mounting cell) and try to obtain a piece of Baader film...

Cristian

[Louis D]

The filter material is probably stressed in some manner.  It may also be too thick to be optically transparent.  Baader Solar Film is really thin and mounted unstressed.  Wrinkles or wobbles in the surface don't matter.  I've been using BSF in homemade cells since it first came out over 20 years ago to good effect.

[Peter Drew]

I would also suspect the original filter.  To me, it looks far too stressed which would easily distort its performance.  Baader film should guarantee a good result.    🙂