Recommendations requested for a wide angle , low power eyepieces for a 8” SCT

[Tropo-Bob (Bob)]

I am thinking of buying a Celestron 8inch SCT (Tube only). I have previously downsized (having previously owned two 12” Dobs & two 8" reflectors), and I have lots of smaller quality scopes, thus, this would be the equivalent of “light bucket” that will fit on existing mounts (largest being an EQ5) and thankfully will not take up much additional space.
I am already in procession of a 2inch focuser that will fit onto the back and also a Celestron 6”/8” dew shield. (I do already have a Celestron 6”, which that focuser will not quite fit!!)
My question is: How well will this set up work with wide-angle, low power, and what is recommend as a low power 2” inch eyepiece (with 3mm to 4mm exit pupil) for such a setup?
I am concerned about the level of vignetting (light-drop off) that I may encounter with a wide angle eyepiece. I know that it is not such an issue with the larger SCTs, but I am uncertain about the 8”size.
A second question, is that given I already have accessories for the Celestron, is there any technical reason why I should consider an 8” Meade SCT instead of the Celestron?

[Merlin66 (Ken)]

The choice of eyepiece is to personal a decision to comment on....
The internal baffle will be the FOV limiting factor....
Re Meade v's Celestron....
I used all the Meade Lx200 series (8"/10"/12") for many years and they worked very well albeit they were very heavy OTA's.
I couldn't fit the 12" on a NEQ6pro so ended up initially with a C9.25 (fantastic!!) and later a C11.
The reduced mirror slop in the Celestron was noticeable and with a Feathertouch 10:1 focuser, a joy to use. Optically they performed very similar.

[casstony]

Since it's to be a wide field light bucket I'd suggest you look at the Meade ACF or Celestron Edge 8" since the outer field is very aberrrated in a standard 8" SCT.

The ideal lowest power eyepiece is a 35mm Panoptic since it's 38mm field stop is about the same as clear aperture of the telescope rear cell.

[Tropo-Bob (Bob)]

Originally Posted by casstony

Since it's to be a wide field light bucket I'd suggest you look at the Meade ACF or Celestron Edge 8" since the outer field is very aberrrated in a standard 8" SCT.

The ideal lowest power eyepiece is a 35mm Panoptic since it's 38mm field stop is about the same as clear aperture of the telescope rear cell.

Thanks for your advice; it opened up a new line of thinking for me. After researching further, I ordered a Celestron Edge 8" and it arrived today, though of course, it is cloudy.

[casstony]

Nice choice Bob, I'm sure you'll be impressed by the views through the scope. Remember to check that the mirror locks are loose before focusing.

A friend has one of these which is outperforming his 5" Tak on planets, though it's likely that there is some variation from sample to sample.

[Camelopardalis (Dunk)]

Congrats on your Edge 8 Bob, love mine, great portable scope

If you have nice dark skies where you are then consider something in the 40mm focal length, like a Paragon (or good clone), Pentax, Panoptic, or Meade/ES equivalent. It maxes out the FOV you can get (about 1.3 degrees or so) and I've not noticed any vignetting with the setup...it's possible I'm just not sensitive to it.

[casstony]

Using an eyepiece with a field stop larger than the C8 rear cell clear aperture (38mm) won't gain any extra field of view, though it will give greater brightness but with less contrast if that's what you're after.

Using a 40mm 68 degree eyepiece with a 46mm field stop, I find vignetting starts to become noticeable with a restriction 3mm smaller than the field stop.

[Tropo-Bob (Bob)]

Hopefully, I will see some stars tonight as the weather is better today.

I have a 30mm Andrew EP with 80 degree field of view. With the new scope, the 30m EP gives good views of the nearby mountain, but of course the stars may be a different story. It seems well illumanted to the edge, even though the field stop is 41mm.

I would love to obtain a better eyepiece, I just don't know what!
Weight, rather than cost is the limitation, but then again, these wide-angle, low magnification eyepieces tend to be expensive, so I want something that really works well. I will consider any EP from 30mm to 40mm.

Meanwhile, I will test the 30mm when possible, and maybe it is good enough!

[Camelopardalis (Dunk)]

If it doesn't look bad, stick with it...it can be a game of diminishing returns and that end of the focal length spectrum usually brings out the heavyweights

Btw, at risk of sounding like a stuck record, the Paragon is nice and sharp in the Edge 8, nothing ugly, and relatively lightweight at about 500g.

[Tropo-Bob (Bob)]

Originally Posted by Camelopardalis

If it doesn't look bad, stick with it...it can be a game of diminishing returns and that end of the focal length spectrum usually brings out the heavyweights

Btw, at risk of sounding like a stuck record, the Paragon is nice and sharp in the Edge 8, nothing ugly, and relatively lightweight at about 500g.

It was better weather last night, so I was able to test the new scope. It was a relief to see that collimination was good, before testing further. My better performing eyepieces were the 24mm Panoptic and the 18mm Radian. That said, the 10mm Radian (200x) worked well on Mars and Double Stars, such as Antares.

The Andrews 30mm eyepiece was too distorted at the edge for my liking, and was not even as clear in the centre as I hoped. However, it was useful for general scaning and locating objects (I am not a Go to user). So I will read up on the Paragon and other eyepieces. If I go that way, where would I buy a Parogon EP from? Currently I am leaning towards the 35mm Panoptic, but I really appreciate opinions from owners on not only what they have found to work well with a SCT at low power, but also on what EPs have been a disappointment.

[Camelopardalis (Dunk)]

Sounds like you're using nice glass there Bon

The original TMB Paragons occasionally show up used in the ice trade classifieds or over on astro mart. Failing that, there are clones from TS ( here ) and SW that are reported to be very good.

Alternatively the ES82 30mm works well (I use one) for an immersive experience, likewise a Nagler 31T5..I've never had the pleasure of the latter though and both are the best part of a kilogram. Likewise, I've never had the pleasure of the longer focal length Panoptics

There's also Pentax XW and XL 40mm and they work well with the Edge series too.

[casstony]

If you have any astigmatism at all stars will look like crosses at low power, in which case an eyepiece with long eye relief is an advantage enabling observing with spectacles. I know the 35 Pan works well in this case, and the ES 34mm 68 degree would probably be good too.

If you don't want to use spectacles then the ES30 82 degree will give identical performance to a Nagler 31 in an Edge scope.

If you want a lightweight eyepiece the Titan II ED 35mm or Skywatcher Aero 35mm are reasonable choices. If you go to a 40mm the real field of view will not be any bigger.

[MattT]

I don't have a SCT but in refractors at f9 11 and 12 and Newt at f4.8 + coma corrector the ES 34mm 68º is real good. No pincushion in the refractors and same in the Newt.
Matt

[Wavytone]

Bob,

Having had both the TMB Paragon 30mm and the 40mm, these will be fine with an 8" SCT - if you can find one. They occasionally appear on Astromart (where I scored mine) and Cloudynights at reasonable prices.

The 40mm should be very nice and comfortable to use, pin sharp stars to the edge and nice eye relief. The 30mm has much less eye relief, in return you get a wider apparent field of view. Of the two I'd pick the 40mm over the 30.

You could of course pay rather more for a Paragon, Nagler or ES.

With the right eyepiece the images in the Celestron 8" Edge HD should be pretty good to the edge, having tried one before.

[Tropo-Bob (Bob)]

Thanks to everybody who gave advice- I eventually decided on a 35mm Panoptic; it should be here on Thursday.

[astro744]

Originally Posted by Tropo-Bob

Thanks to everybody who gave advice- I eventually decided on a 35mm Panoptic; it should be here on Thursday.

Excellent choice! Well done!