Goodbye Celestron C8 - not for the faint hearted ...

[AstroRookie]

Hello,

as I'm starting astrophotography on a budget I recently successfully astro-modded a second hand Canon 500D (did not have the chance to test it under the night sky tough, bad weather for several weeks now). Referring to my username, I considered this a major achievement. But I pushed my luck, and while trying to check out the backfocus with the DSLR-coolbox I'm making, by attaching it to the C8 OTA, I pushed the C8 from my desk. It fell straight on the front, it was even  standing upright. Then I lifted it up ... the horror ... see attached picture.

I looked how much it would cost to replace it, found this site: schmidt cassegrain corrector plate - 380€+transport

Taking into account:

• a F/10 sct is not ideal for astrophotography (I bought a focal reducer tough, but still)
• This scope is 23 years old (optics were still ok ... till today) and spending 380€+transport, to fiddle for several nights to get things adjusted correctly, would be waste I think
• Focusing is not ideal either with this thing
• I was planning to buy a new scope in a year or two (considered, if I can make something out of this setup - SCT C8 with old DSLR - then I could upgrade to something "decent")

Now my questions:

• Can I sell this OTA with the damaged corrector plate?
• I'm considering to buy a 8" F/4 Newtonian to replace it (a decent refractor is way too expensive for a "transition" scope), any advice?

Kind regards,

AstroRookie

[NGC 1502]

Sorry to hear of your misfortune.....you could check the site you linked to and see if they could repair and the cost.

My best guess is that it would cost less to find a second hand replacement than to repair the damaged one, and probably much quicker.

You may find a buyer who could buy your damaged scope for parts.  If the secondary and primary mirrors are ok, there’s the focusing mechanism etc. Possibly the link may offer a price to buy.

Hoping you find a solution, Ed.

[Robindonne]

Try making a classic cassegrain from it

[NGC 1502]

Just now, Robindonne said:

Try making a classic cassegrain from it

I thought the front corrector was a necessary part of the optical system.....

[Robindonne]

8 minutes ago, NGC 1502 said:

I thought the front corrector was a necessary part of the optical system.....

You’re right.  
 

Its sorry to see.  But these damages will probably never be repaired.  The cost of a used c8 is the same or even less than a new Plate

Edited August 30, 2020 by Robindonne

[Tenor Viol]

The primary mirror is spherical not parabolic.

The corrector plate gets its name from the fact it 'corrects' the spherical aberration of the primary. You would need to get a secondary that as well as bringing the image to the correct focus can do the work of the corrector plate and fix the spherical aberration. I'm not an expert on optics, so not sure what your options would be in that regard, but I suspect not cheap.   

Edited August 30, 2020 by Tenor Viol

[John]

Would your insurance cover it ?

 

[Craney]

Ouch !!..... 

Well, yes I know the pain.  I did something similar with a Meade 8 inch SCT, but here is the interesting part, I manage to damage the  primary  and secondary mirror, but not the corrector plate !!!

I'll let you you guess what happened.

I keep the 'remains' in a box and dare not look at them...... it is still too sensitive a topic.

Anyway,  it would be interesting to know if a Meade Corrector plate would fit and work on a Celestron C8..... because if it does then we can talk some more , and who knows, your C8 may image again.

Maybe somebody on here who knows about SCT's can chip in... (??).

Regards,

Sean.

 

[NGC 1502]

15 minutes ago, Craney said:

 

Best person I can think to ask on here is Peter Drew.   Or optical guru Es Reid, he does optical testing for our sponsors FLO

 

Edited August 30, 2020 by NGC 1502
Correction

[Pixies]

1 hour ago, John said:

Would your insurance cover it ?

 

That's what I was about to say! Worth checking.

[RT65CB-SWL]

Oh gosh! 

On 30/08/2020 at 18:28, John said:

Would your insurance cover it ?

 

When I had the mishap with my ETX105, before the 'remod', my home contents insurers at the time were very stubborn and refused to pay and/or replace. They said something on the lines of... 

"Dear Mr P. J. R***e,

Thank you for your telephone enquiry of [date] and postal correspondence of [date].

On this occasion and with regret that we are unable to replace your telescope and/or for damaged parts; (i.e. damaged ABS plastic rear end, etc., as per the completed claim form and as shown in your included photos), as the damage to your telescope happened within the confines of your garden, unless the damage was within the premises of the insured. [I presume they meant inside the home]. Please do not hesitate to contact us if you wish to discuss your claim, where one of our qualified agents/representatives are willing to assist you."

I promptly changed my home contents insurers upon the renewal date which was due a few months later.

Edited September 2, 2020 by Philip R

[AstroRookie]

8 minutes ago, Pixies said:

That's what I was about to say! Worth checking.

Hello Pixies,

don't think so, insurance only covers glas damage of the building. If somebody else, well that is apart from my spouse, say a friend who was visiting us broke it, then her/his insurrance might cover it. But it's me who broke, and i have to bare the consequences. And I almost made up my mind, I'll replace it with a new newtonian.

But thanks for the advice.

AstroRookie

[Louis D]

You could try masking off the broken part and see how objects look when viewing the night sky.  It costs nothing to try (except for the cost of some blue masking tape), and it might yield surprising results.

[Shimrod]

2 hours ago, Philip R said:

On this occasion and with regret that we are unable to replace your telescope and/or for damaged parts; (i.e. damaged ABS plastic rear end, etc., as per the completed claim form and as shown in your included photos); as the damage to your telescope happened within the confines of your garden, unless the damage happened within the premises of the insured." [I presume they meant inside the home]. Please do not hesitate to contact us if you wish to discuss your claim, where one of our qualified agents/representatives are willing to assist you."

I promptly changed my home contents insurers upon the renewal date which was due a few months later.

It's always worth reading the definitions within the policy booklet. Mine (UIA) has separate definitions for Home and Premises - the latter includes the garden and all outbuildings within the boundaries of the property.

[Peter Drew]

As Louis D says, mask off the broken area and give it a try except I would rather black out the lines which would result in a Newtonian spider effect.  The optical power of the corrector, although essential is fairly weak and the damage may be less severe than would appear.  I doubt whether a replacement corrector plate would be perfectly compatible with a C8 of that vintage as I'm pretty sure in those days the optical components were individually matched.  In any event, as mentioned a used one from the period would be cheaper to buy,  I bought a complete 1980's C8 for £250 and the optics are excellent.  I think you have already decided to invest in a Newtonian which is likely to better suit your imaging purpose.     🙂

[AstroRookie]

@Louis D @Peter Drew

I thought about that, but there are small pieces of glass in the OTA, so I'm afraid that pointing it to the sky might spread these pieces of glass over the primary mirror. A guy from a telescope shop, where I did an inquiry for a new scope, told me "it can only be used as an umbrella stand". I'll maybe put it on a second hand site for astro-equipment, and ask a "symbolic" 20€ for it, one never knows if somebody could use it for the spare parts.

The initial idea was that I'd replace it within 2 years from now, after I gotten some experience with imaging. So now I was "forced" to buy a new one earlier and on a tighter budget (and the dedicated astro-camera will have to wait ...). So I ordered the Orion 8" f/3.9 Newtonian Astrograph Reflector. Of course I also needed to buy the coma corrector and laser collimator. But for under 1000€ I think that was the best I could get. I now I stop mourning about, it is what it is.

Kind regards,

AstroRookie