Eyepiece upgrade

[kon1966 (Kon)]

Hi all,
Have a 8se with 6.3 reducer, looking to upgrade eyepieces. Currently have...
Bintel 40mm plossl
Bintel 32mm plossl
Bintel super wide 20mm
Bintel super wide 15mm
I want to upgrade the eyepieces so putting aside budget constraints, what is a good upgrade and looking for increased contrast and sharpness.

Regards
Kon

[astro744]

8" SCT at f10 (2032mm)

24mm Panoptic for 85x and 0.76 deg field.
13mm Nagler for 156x and 0.5 deg field.
9 mm Nagler for 226x and 0.35 deg field.

8" SCT at f6.3 (1280mm)

24mm Panoptic for 54x and 1.2 deg field.

13mm Nagler for 98x and 0.79 deg field.
or
16mm Nagler for 80x and 0.99 deg field.

9 mm Nagler for 142x and 0.56 deg field.
or
8mm Delos for 160x and 0.44 deg field.

7mm Nagler for 183x and 0.43 deg field.
5mm Nagler for 256x and 0.31 deg field.
or in lieu of 7 and 5
6mm Delos for 213x and 0.34 deg field.

Note I have a C9.25 and f6.3 reducer and never use the reducer visually. I bought a 2" visual back and use a 41mm Panoptic for my low power widest true field view. The 35mm Panoptic is also a very good choice as it is a lot lighter. Note you cannot use the f6.3 reducer and 2" visual back with 2" start diagonal and 2" eyepieces as it just does not work. You cannot reach focus even by shifting primary mirror and I'd say even if you could reach focus there would be vignetting.

If you stay with 1.25" then the 24/13/9 combination just cannot be beat either with or without the f6.3 reducer and if using it then add the 7mm and/or 5mm Nagler for a bit more power.

[Renato1 (Renato)]

For a cheap upgrade and additions:

In my C8, my most used eyepiece (for faint stuff) was a 20mm Erfle. Recently, after 20 years I got something a bit sharper - a 19mm Flat field eyepiece of the type sold by Smart Astronomy, Orbinar and numerous others. I also have a Meade 18mm UWA, which is fine, but the eyepiece is big.

For looking at planets -
a 10mm eyepiece (200X useable most nights)
an 8mm eyepiece (254X for when the seeing is better)
a 6.4mm eyepiece (320X for the lesser number of nights, when that power is useful)
a 5mm eyepiece (400X for those few nights a year, when I can get a decent image at that power)

If you have a 2" diagonal, surprisingly, even a cheap 30mm Ultra Wide Angle eyepiece gives pretty impressive views (providing you don't mind distortion at the edges). Bintel and Andrews used to sell one for $80, which had a Barlow screwed into it to give 20mm (but with the Barlow attached, it was only a Superwide angle eyepiece). But a more expensive one will be better, obviously.

Alternatively, a 2" 40mm Superwide angle eyepiece, will be heaps better than a 1.25" 40mm eyepiece (I tend to use mine with a broadband LPR filter to get rid of skyglow)

The f/6.3 reducer I didn't use much visually because at the effective 20mm eyepiece focal length (20mm without reducer, 12mm with reducer) I didn't see galaxies as well. But that doesn't matter so much for brighter objects.

So what I am suggesting is
0.5 to 1mm exit pupils for high power,
2mm exit pupils for galaxies and other faint DSOs,
4mm exit pupils for wide bright field,
3mm exit pupil with an Ultra Wide eyepiece because I like it.

With your focal reducer and a 40mm eyepiece, you can get a big 6.3mm exit pupil. But I've only ever found that useful once - when trying to see the Horsehead Nebula with a H-Beta filter.

Good luck with whatever you choose.
Regards,
Renato

[Steffen]

Originally Posted by Renato1

With your focal reducer and a 40mm eyepiece, you can get a big 6.3mm exit pupil. But I've only ever found that useful once - when trying to see the Horsehead Nebula with a H-Beta filter.

Did you actually see it in the C8?

Cheers
Steffen.

[Renato1 (Renato)]

Originally Posted by Steffen

Did you actually see it in the C8?

Cheers
Steffen.

Yes - but it was faint and I had to put black cloth around my head and the eyepiece. And it definitely wasn't as good as in my 14.5" dob, that I got a year or two later. But I did see it with a bit of staring.

So all up, I've seen the Horsehead, the Comma under the Orion Nebula and one other non-famous nebula using the H-beta filter. Not really a good investment.
Cheers,
Renato

[Steffen]

Not a good investment? I'd say that's pretty darn good for an 8" scope. I've only ever seen the Horsehead through Mental's 17.5", twice, the second time was really difficult.

Cheers
Steffen.

[Amaranthus (Barry)]

I regularly use the f/6.3 in my C8 when doing DSO visual - it gives me a lovely wide and flat field. I use a Panoptic 24 and Nagler 16, 11 and 9, and PowerMate 2.5x (yielding a magnification range of approx 50 to 150 [and 200 to 350 with the PowerMate]. It makes a great combination. It stays in for DSLR imaging, of course.

When I'm doing planetary (including webcam) or double star work, I take the reducer/corrector out. Flexible - like two telescopes in one.

Tonight I collimated at 850x using a PM2.5 and 6mm Plossl. Nice Airy pattern

[Renato1 (Renato)]

Originally Posted by Steffen

Not a good investment? I'd say that's pretty darn good for an 8" scope. I've only ever seen the Horsehead through Mental's 17.5", twice, the second time was really difficult.

Cheers
Steffen.

That's very strange. My filter is the original Lumicon one.

It was 16 or so years ago now, when I took my 14.5" dob to a club night at the Briars (Mornington Peninsula Astronomical Society site) - which isn't very dark - and I used a 26mm plossl which gave a 5.8mmm exit pupil. There were about a dozen people there, and all but one saw it without difficulty. The one who couldn't see it kept being given instructions by the others on where to look in the field of view, but it was to no avail, he couldn't identify it.

From everyone else, there had been a stream of "Ahs" as they spotted it.

Could it be that too small an exit pupil was being used on the 17.5" dob you were looking through? The instruction that came with the filter said a 6 to 7mm exit pupil is required.
Regards,
Renato

[Steffen]

Originally Posted by Renato1

That's very strange. My filter is the original Lumicon one.

What is strange? The Horsehead being an elusive object? I'd say that's in line with what pretty much everybody says.

It was 16 or so years ago now, when I took my 14.5" dob to a club night at the Briars (Mornington Peninsula Astronomical Society site) - which isn't very dark - and I used a 26mm plossl which gave a 5.8mmm exit pupil.

Have you seen it since?

There were about a dozen people there, and all but one saw it without difficulty. The one who couldn't see it kept being given instructions by the others on where to look in the field of view, but it was to no avail, he couldn't identify it.

Maybe he was the only honest chap of the bunch?

From everyone else, there had been a stream of "Ahs" as they spotted it.

Yeah, I get that too sometimes from people who didn't even find the eyepiece...

Could it be that too small an exit pupil was being used on the 17.5" dob you were looking through?

I'm not entirely sure which eyepiece we used, but it was the best one available for the task at hand, I'm quite confident of that. Alex put an OIII+Hb filter in, as far as I remember.

Cheers
Steffen.

[Renato1 (Renato)]

Originally Posted by Steffen

What is strange? The Horsehead being an elusive object? I'd say that's in line with what pretty much everybody says.



Have you seen it since?



Maybe he was the only honest chap of the bunch?



Yeah, I get that too sometimes from people who didn't even find the eyepiece...



I'm not entirely sure which eyepiece we used, but it was the best one available for the task at hand, I'm quite confident of that. Alex put an OIII+Hb filter in, as far as I remember.

Cheers
Steffen.

It was a members night, not a public night for newbies - everyone there owned telescopes and were experienced users. I just happened to have been one of the first to buy what was then an expensive filter.

I suspect that if an eyepiece giving a 6mm exit pupil or larger had been used, then the problem with the 17.5" lies with having stacked the O111 filter with the H-Beta. The O111 dims the image. It doesn't matter that it lets most of a band of light through, it still dims it. Every time I've tried any combination of stacking filters, including broadband, UHC and O111, the result has been junk - way too dim.
Regards,
Renato

[astro744]

Stack a H-Beta with an O-III and you get almost nothing through as the peak wavelength and narrow bandwidth for each do not coincide. That's the whole idea to let through only the wavelength you are after. Note the UHC includes both H-Beta and O-III lines but stacking the latter two does not give you a UHC since each filter excludes the other one from its bandwidth.

Back to the original post, note the request was to put aside budget constraints.

I would also recommend the entire Tele Vue Plossl range for increased contrast and sharpness as an alternative to the other Tele Vue eyepieces I suggested earlier. Another option would be for some orthoscopics from Kokusai Kohki but it depends on what style of eyepiece you want.

I have briefly compared the 6mm Clave Plossl, 6mm Brandon Orthoscopic and 6mm Radian (and yet to directly compare the 3-6 Nagler Zoom) and I can tell you that out of all of these the 6mm Radian is the most comfortable with its big eye lens and plenty of eye relief and did not show me any less than the other eyepieces, (target was Jupiter at 273x through 10.1" f6.4). I do not have a 6mm Delos or 6mm Bintel/GSO Plossl to try.

Note the 24/13/9 combination for an 8" SCT is also recommended by Tele Vue at http://www.televue.com/engine/TV3b_p...7#.U3A5-IGSy5I

[Steffen]

Originally Posted by Renato1

I suspect that if an eyepiece giving a 6mm exit pupil or larger had been used, then the problem with the 17.5" lies with having stacked the O111 filter with the H-Beta.

Not stacked, one filter that passed both bands.

Cheers
Steffen.

[Renato1 (Renato)]

Originally Posted by Steffen

Not stacked, one filter that passed both bands.

Cheers
Steffen.

Thanks, I didn't know such a filter existed.
In my opinion, the problem lies with either the filter or the exit pupil used.

As a C8 can show the Horsehead, it should be cinch in a 17.5".

To the OP, sorry for this digression in your thread.
Cheers,
Renato

[kon1966 (Kon)]

The televue's are great but at $300+ each, the minister for everything will send my you pair of know whats to the moon. But the Orion Stratos Ep are in my budget. Have read reviews last night and they seem ok. Still stick to the 24/17/8 rule with a barlow.

Has anyone had any experience with them on sct.

regards
Kon