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Using 100 degree eyepieces with an 8" f/10 SCT

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#26 Tfer

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Posted 16 September 2020 - 01:05 PM

Some added thoughts on the focal reducer, based on my experience using one with my C8 on a fork mount:

 

- Larger eyepieces and 2" diagonal no longer clear the bottom of the fork mount...Doh!

- Larger eyepieces and 2" diagonal no longer balance due to added weight and moment arm

- Threads on reducer are contemporary "loose tolerance" threads, don't go on to older C8 without some protesting...not cool

- Switching to high magnification requires taking off diagonal, taking off reducer, replacing diagonal, then switching eyepiece...that's a hassle

- most important: with longer optical path length of 2" diagonal...I couldn't achieve focus at infinity, so I need to bring that second 1.25" diagonal

 

These are the reasons I no longer own a 6.3 reducer.  I'm of the opinion that longer eyepieces are the way to go.

 

I hope that's useful.  Cheers!

My reducer doesn't leave my 8SE.  The only way that it reduces contrast, is by widening the field of view.  If I am going after Mars on a good night, I have both the eyepieces and Barlows to accomplish it.



#27 SeattleScott

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Posted 16 September 2020 - 01:23 PM

Using a reducer and a barlow together will definitely impact contrast. It might be a subtle difference and you might not feel it is worth the hassle for a little sharper view. Personally I have noticed increased reflections on the Moon in particular when using a reducer or coma corrector. If the reflections are there on the Moon, they are there on Jupiter too, just less obvious. Personally, I don’t really consider my coma corrected newt or my Mak with reducer planetary scopes. If I happen to have them out and the planets are up, sure I will take a peek. Even if the views are disappointing compared to the usual they are still showcase targets and worth a look. But the views are noticeably worse than say my 4” Apo or the Mak without reducer. Consequently I tend to not get out my coma corrected newt or Mak with reducer if the Moon and planets are out.

That being said if you are more a DSO guy and more of a casual lunar/planetary guy, you might be happy with the trade off. I certainly remember getting nice views of Mars with my old SN8 (no reducer but far from an optimal planetary scope). I know many reducers live in the scope and never leave for anything. But make no mistake, there is some impact when you add that much glass to the light path.

Scott

Edited by SeattleScott, 16 September 2020 - 01:32 PM.


#28 Mr Dobson

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Posted 20 September 2020 - 06:20 AM

The pricing of all ES eyepieces have increased recently. I have the 20mm, 9mm, and 5.5mm and love them for the wider views. Check the CN classified ads; they can be found from time to time. Same goes for TV.

Edited by Mr Dobson, 20 September 2020 - 06:21 AM.


#29 SeattleScott

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Posted 20 September 2020 - 09:00 AM

Except the last time I saw the 9mm 100 in the classifieds it was listed for around $400. When these were $300 new they were worth considering. But now they are twice as much as APM and don’t seem to really be any better.

Scott

#30 csrlice12

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Posted 20 September 2020 - 10:37 AM

I think I paid $199 for the ES100 14mm (and the 20 too) when they first came out...the 1.25" ones were $99 each.




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