Celestron Solar Filter for C8 SCT (#94128)

[rwg]

This arrived today courtesy of 365Astronomy and Royal Mail, so I thought I'd write a little bit about it.

Here's the manufacturer page : Solar Filter (for CPC 800, NexStar 8 SE) (item #94128) / Filters / Accessories / Products / Celestron.com

Firstly I have to say that the price is excellent at ~£30 + delivery. I feel that this is incredibly good value for a brand name accessory.

I was attracted to this particular filter due to its design, which attaches to the front of OTA in the same manner as the corrector dust cap - i.e. with a push and twist. I felt that this would ensure a secure fixing of the filter with no chance of it becoming accidentally removed.

The filter arrived well packaged in its own box packed within an outer shipping box. The box containing the filter had warnings on regarding solar viewing and an odd statement that you should check the filter before removing it from its plastic bag as it cannot be exchanged after. This would have made more sense if the bag was sealed in any way, but it wasn't... Odd.

On to the filter itself - it's the outer ring portion of the corrector dust cover from an 8" SCT with an aperture in the plastic of ~ 7 inches. This aperture is covered by a sheet of Baader Solar film, which is glued to the back side of the outer ring. On mine, the film was not stuck down well for a portion of the perimiter. A little pressure seems to have held it in place, but if it seems not to be holding it would be easy to add additional glue or tape without spoiling the aperture portion of the film.

The filter is a very good fit to the front of the OTA - a tighter fit in fact than the dust cover. It certainly feels securely held.

Having never done any solar viewing before, I can't give expert comments on the views through the filter. However, looking both directly through the filter with the naked eye and through the telescope, the sun was visible as a sharp, white disc. No sunspots were visible as far as I could tell, and I was unable to see granulation, even when pushing the magnification to 250x. However, as likely as not that is down to the limited time I had available and my inexperience with solar vieweing.

Before receiving the filter, I'd been wondering how to find the sun, since I'd not be able to use the red dot finder. However, it turned out to be really easy - all I used was a white piece of paper held perpendicular to the metal body of the OTA near the rear cell. Move it around the OTA and look at the size of the shadow on the paper cast by the raised plastic surround to the corrector - when the shadow is equal on all sides, the scope is pointing to the sun.

Overall, I'm impressed with the price point for this filter, along with the solid attachment mechanism. The slight flaw in the glueing of the solar film is a worry that I'll have to keep an eye on, possibly an indication of quality issues in manufacture, or possibly just a 'friday afternoon' job. Anyhow, a DIY fix should be possible if necessary avoiding the need to return the item.

Overall, quite pleased so far and looking forward to getting some more time using it.

Robin

[michael.h.f.wilkinson]

Interesting report. Might get one myself

Cheers

Michael

[kris h]

That will be good for the transit of venus 2012 so dont miss it because the next one not till 2117

[michael.h.f.wilkinson]

I have a glass solar filter (Thousand Oaks, I think), but some say these are not as good. For that money I will be happy to have two types to choose from.

[kris h]

Hi michael

is there a big difference between a glass and a normal filter

[Merlin66]

I use the 1000 Oaks, and JMB glass solar filters as well as the Baader Solar film. Other than the colour cast of the sun's image I haven't noticed any significant difference in the optical quality between them. So on that basis the Baader wins on price!!!

[kris h]

Thanks merlin you justed saved me a bit of money

[michael.h.f.wilkinson]

I bought the 1000 Oaks based on colour and durability, mainly because colour correction of 35mm slides is not really an option. I have heard the Baader Solar film is better optically, but Merlin says there is no great difference.

[Virgoman]

Hi all,

Just thought I would add my tuppence worth. I have purchased the same filter from Harrison Telescopes for £31 inc. delivery and great service. I can concur with what rwg has said. Fits nice and snugly on the C8 - as dust cap does. Provides a nice sharp, white, solar image. Well worth it.

Best Regards,

Ralph