Even lower power EPs - better at 2" ?

[-Aldebaran-]

Julianfr,

I think if you were looking into the maxvisions 82° 28mm you probably wouldn't have seen it as I think it only comes as a 68°

[JulianFR]

Not sure how I missed it, but I've found the 28mm Maxvision now on the ES site. As mentioned I have the 24mm version and really like it. Not sure if there would be much apparent difference between 24 and 28mm. But at 95 euros it is a hood price I think.

Any thoughts on the merits of the SW 32mm Panaview v the Maxvision 28mm?

[crashtestdummy]

I would still look for a second hand ES 30mm 82°.sold mine for less than £150.there was a 28mm nirvana on ABS for about £130 but at that price it would be gone pretty quick

[JulianFR]

I'll keep my eyes on the 2nd hand sites (and SGL).

[russ.will]

I had the 30mm ES82 30mm, which replaced a 32mm Panaview and currently have the 24mm 1.25", 28mm 2" and 34mm 2" Maxvisions.

Forget the Panaview - It isn't even remotely in the same class as the Maxvision or ES82 EPs. It was okay in my F5 200p, but the extra illumiation of the the 300p tore it apart.

Part of me still regrets flogging the the ES82 30mm as it is a truly fantastic EP, but I did find it hard to justify as I was mostly using it as a finder EP. Once the 24mm 1.25" MV arrived, I found that it was getting used more for a couple of reasons. For one, I found that the ES82 30mm was only getting used with a coma corrector in my (then) 12" SW Dob - Some fainter fuzzies were hiding in the outer 20% FOV without the CC and I also found that the levels of eyeball swivelling to actually see that extra FOV was uncomfortable. The other reason was that I couldn't be bothered with faffing about with taking the 2-1.25" adapter in and out.

As such and this may be flying against the grain, but I'd suggest you ignore the 28mm MV and simply get the 34mm for finder purposes. The 28mm is too close to the 24mm to be useful (I have both) and the 34mm whilst slightly too long in an F5 Dob (6.8mm exit pupil) it is perfectly usable in the finder role. Being 68deg, it is dead easy to use without being a coma nightmare - Certainly no worse than the ES82 30mm and a fraction of the price.

Russell

[abberation]

I have read this topic a few times and find all the posts very informative. I understand now about maximum exit pupil / maximum dilated pupil but how do you measure/determine your maximum dilated pupil. (dont want her anywhere near my eyes with a retractable steel tape).

[bingevader]

I don't know about measuring it, but there is a estimated exit pupil calculator here, about half way down. 

[Alien 13]

I have a stupid question does the exit pupil actually matter i would love to be able to get down to magnifications of 5x or below.

Alan

[John]

I have a stupid question does the exit pupil actually matter i would love to be able to get down to magnifications of 5x or below.

Alan

If the exit pupil is larger than your dilated pupil, some of the light collected by the primary mirror / objective lens isn't getting in to your eye so it's the equivalent of using a smaller aperture scope.

Whether that matters or not is up to individual preference I guess.

It's supposed to be less of an issue with refractors according to Al Nagler although it still seems sensible to me to keep the exit pupil to a usable size.

[abberation]

I don't know about measuring it, but there is a estimated exit pupil calculator here, about half way down. 

Ben thanks for that Rich

[rwilkey]

Hi Julian, i am a bit late in on this thread, but if you want to borrow any of the ep's mentioned above I have them except the 38mm Pan.  Just give me a buzz or drop me a line.

[JulianFR]

Robin, many thanks for the offer. That is very generous of you...it would be great to borrow one of your low-power EPs. I'll be in touch!

[JulianFR]

I see there's a Baader Scopos Extreme 35mm 2" for sale in the classifieds. Anyone know what that would be like with an f4.9 reflector (or f5 refractor)?

[JulianFR]

Hi everyone... Any thoughts on the Baader Scopos 35mm for use with a 300 Flextube? 

[rwilkey]

Hi Julian, in your Skyliner that would give an exit pupil of 7.09 which might be just about manageable, but I wouldn't risk it. True field 1.628 degrees. 32mm is the limit I think.  In your Startravel 120, the exit pupil would be 6.04 which is much better as you would expect.  Too much of a risk in my opinion.

[JulianFR]

Got it... Thanks Robin. Very helpful as always. I hope to be at June's Swindon Stargazer's meeting so maybe I can corner you there for more tips ;-)

[AlexB67]

Julian, AFAIK, some of the issues with the too wide exit pupil seems to be that you can start seeing the secondary as a tiny soft spot in the centre. Can't say I've ever noticed it since I always refrained from buying an eyepiece with that huge an exit pupil. But I have read of reports where people find it hard to use in such cases.

The other thing may be a factor, and this will depend on your skies, if you have a bit of light pollution the views will become washed out too with wider exit pupils making fainter objects hard to detect.

My Maxvision 28mm which has an exit pupil just under 6mm which small enough to be less than my eye pupil, but that washed out effect can be observed under my poor home skies.

If the exit pupil exceeds the your dilated eye pupil you wil begin to waste aperture as well. Now a few fractions of a mm here or there will hardly matter much, but if it is 8mm and your eyes dilates to 6mm it will result in more significant light loss.  If using it as  a finder again no big deal a lot of the time, however for detecting faint stuff you may not see what you are looking for. I get this from home under my LP skies, where I have had it happen to me not being able to detect some galaxies at all,  then I pop in an eyepiece with a smaller exit pupil around 2 - 4mm with  a darker sky background, and an object can pop into view and become detectable with averted vision.  Quite fun when that happens mind you