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Bought my first SCT! - Need some Advice

nmoushon

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Owmuchonomy

Owmuchonomy

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Lots of good stuff has been said. I must be very lucky as mine seems to be well collimated after 7 years of use so my point is check the view first before you invest in collimating gear. The 40mm Celestron omni plossl is the bargain of the century for this scope but then I also sometimes use my ES 28mm 82' with the Baader click lock 2" back. My worst enemy, dew, dew and more dew so I purchased a Kendrick dew band. Excellent investment.

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RT65CB-SWL

RT65CB-SWL

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...Finally, store it pointing upward. The primary mirror slides on a grease covered tube. You don't want a lump of that falling on your secondary because it got a bit warm one day.

Russell

Sent from my iPad using Tapatalk HD

I must remember to rearrange my SCT trolley flight case so that the corrector plate is pointing upwards when transporting it - thanks for the advice!  :icon_salut:

I found a very small 'blob of goo' too on my ETX105 meniscus cell a week ago.  :icon_frown:  What is the best way to clean it? (...and the mirrors, (primary & secondary). They are little bit dusty! - though it does not spoil the views as I have read and heard that the propellant in compressed air duster cans can/may ruin the coating).

BTW - the ETX105 is stored in a handheld flight case.   

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Dave In Vermont

Dave In Vermont

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I don't know, Philip. If it's an SCT-type scope (like the ETX), he may well of had a hand in it. People would ship their SCT's to him from all over the map. Aside from fixing those that got hurt, he did a service called "Hypertuning" which people swore by. It would make a scope work like a Swiss Watch. I don't know if he still does this. He must be getting on in years by now. But his mind is sharp as a tack.

Here's his website:

http://www.arksky.org/index.php

Lots of valuable information there you won't easily find elsewhere,

Dave

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nmoushon

nmoushon

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Thanks for the added advise everyone, much appreciated.....though I'm sure my wife wouldn't say the same as I'm now already saving up for several extras.  :grin: Though I do have a couple new questions now though.

If I get the 2" back will that effect what kind of crayford I get in the future or do they all fit the same regardless of what back I get?

I am currently  storing the scope inside my house in a spare bedroom (so no worries about heat) but it is "standing" with corrector plate on the carpet(it does have the end cap on it) when it is outside the box. Is that an appropriate way to store it? Or should I try and keep it in the box where its laying horizontal whenever possible?

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nmoushon

nmoushon

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Another thought....which is "better"? Wide EP like 30-40mm or wide FoV like 60-80 degrees?

Also is a 1.25" EP that is 40mm and 80 degrees FoV comparable to a 2" EP that 40mm but at a more normal FoV of 40-60 degrees? The wide EP with wide FoV get very expensive and trying to find a suitable alternative. 

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Stu

Stu

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Another thought....which is "better"? Wide EP like 30-40mm or wide FoV like 60-80 degrees?

Also is a 1.25" EP that is 40mm and 80 degrees FoV comparable to a 2" EP that 40mm but at a more normal FoV of 40-60 degrees? The wide EP with wide FoV get very expensive and trying to find a suitable alternative.

To get one thing correct, it's not possible to have a 40mm 1.25" 80 degree eyepiece because of the limitations of the field stop within the 1.25" barrel.

The largest fov in a 1.25" format is roughly as follows:

40mm 43 degree afov

32mm 50 degree afov

24mm 68 degree afov

So that's one reason to go with 2" because you can actually achieve a larger true fov with that format because of the larger field stop/barrel size.

Second point, I would say it is better to have a wider afov eyepiece in a shorter focal length eyepiece, exactly what you don't want to hear!!

The main reason is that you will see the same area of sky in say a 24mm 68 degree afov vs a 32mm 50 degree afov Plossl, but the exit pupil will be smaller in the 24mm so your sky background will be darker and apparent contrast of stars will be better.

Another example might be to show the benefit of the ultra wide eyepiece in 2" format.

In a 200mm aperture, 1000mm focal length scope, a 24mm 1.25" 68 degree eyepiece would give x41 mag with a 1.63 degree field of view and a 4.8mm exit pupil

A 21mm Ethos would show more sky at a higher mag and smaller exit pupil ie x47, 2.1 degrees of sky and a 4.2 mm exit pupil. So the 2" ultra wide shows more sky with the darker sky background.

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nmoushon

nmoushon

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Another quick question. I was looking into a 2" Diagonal for my scope and noticed that there are "refractor" style diagonals and "SCT" style diagonal. The SCT ones that I've seen have screw cap instead of noise piece like the refractor style. I understand that this is needed so that if it is mounted of a fork mount it wont knock into the base but since I have mine mounted on a GEM do I have to use the SCT style diagonals or can a refractor style work with SCT as well? I would like to be able to switch the diagonal over to my ED80 instead of having to buy 2. I'm at work so I can't go check the scope myself to see if I can figure it out myself. Thanks.

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