Louis D

5 hours ago, miguel87 said:

If you need to go further in, you must use a barlow lens or alter your focusser arrangement in some way.

I reach focus using a GSO coma corrector attached via a T-thread to M48 thread adapter.  It also flattens the field and corrects coma at the same time.

3 hours ago, John said:

I'll look forward to your feed back on the SW "variable" Dave

The ONLY 80 degree variable / zoom around as far as I'm aware.

 

Technically, there is also the 8.5-12mm Speers-Waler Zoom Eyepiece.  Here is David Knisely's review of it.

I have had the original 5-8mm for about 20 years since new.  It is very sharp across the field, but it is pretty tight on eye relief for an eyeglass wearer.  My eye astigmatism doesn't clean up until close to the 5mm end, so it's more of a variable plossl to me.

I would extend the legs quite a bit more to provide more guard-band stability against accidental tipping in the dark, especially if you're going to use it on a hard surface as shown rather than on grass.

Since the 250PX has a 25% central obstruction by diameter compared to 31% for the 8SE, it should provide better contrast on planetary details.  However, the 180PRO has a 23% obstruction, and so should be slightly better than the 250PX.  On the other hand, there are far more surfaces involved with the two CATs than with the Newt, so it comes down to quality of figure and polish in each scope.  That, and the obvious aperture differences between them.

For reference, the best planetary views I've had were through a 12.5" Mag1 Portaball with a Zambuto primary under steady seeing conditions.  Jupiter looked about like one of those photographs created from lots of combined frames.  There were all sorts of ovals, festoons, and barges.

I think you're missing a T-thread to 1.25" adapter to attach your T-ring to your barlow.

On 04/05/2020 at 08:52, merlin100 said:

I've already got the Sky-Watcher Skyliner 200P Dobsonian. 😉

Avoid achromats then.  If you're used to the sharp, color-free image of a reflector, you won't like the reduced contrast inherent in an achromat because all the colors don't focus tightly together.  I'd look for a used 72ED scope and a decent side-mount alt-az unit to go with it.  It will nicely complement your Dob.

I bought an ST80 20 years ago and couldn't stand the poor images, so I rarely used it.  About 7 years ago, I bought a used Astro Tech 72ED and absolutely loved the pin sharp stars in it.  So much so, I bought a used 90mm TS APO triplet recently to gain a bit in light gathering and color correction without getting too much larger.  However, it cost 4 times as much as the 72.

If that scope has a 2" focuser, I'd recommend the 30mm APM Ultra Flat Field for wide field scanning and observing.  I measured mine as having a 73 degree apparent field of view and it is quite sharp at f/6.  I've read reports of it being sharp to the edge to at least f/5.  It is easy to use with eyeglasses.

The GSO/Revelation 2x ED 2" Barlow comes with a 2" to 1.25" adapter that recesses into the 2" tube via a notch on the side.  It then has a recession in it to allow most 1.25" eyepieces to be roughly flush with the top of the 2" tube so they will remain parfocal with 2" eyepieces.

3 hours ago, DaveL59 said:

After all if it gets re-sold it'll be as a customer return and maybe mention the chipped secondary so nothing to lose really.

Depends on the retailer.  There was a thread about a damaged eyepiece or lens in the distant past being returned to a NYC retailer with a handwritten note describing the damage tucked in the bottom of the box.  Someone else on the same forum got that same item shipped to them as new with the other member's note still tucked in the box.  The retailer just treated it as an ordinary return, not a damaged goods return.

I brought along my 32mm GSO/Revelation Plossl to Nebraska for the 2017 eclipse where it worked fine for widest field views in my ST80.  It has very sharp optics, great coatings, a sharp field stop, and is very reasonably priced.  I've never had blackout issues with it, either.

6 hours ago, robhatherton said:

Yes I expect I’m not really comparing the edges of the field as I should. Anyway I’m looking forward to upgrading to an Ed or apo frac next birthday!

Thanks!

That's the way to do it.  Start out with what you can afford and gradually upgrade your equipment while you learn the skies and observing skills.  For me, my backyard trees grew up and blocked most of my views and my town grew from 4000 to 80,000 people in 25 years, so I'm having to look at relocating to continue observing in the future.

14 hours ago, JTEC said:

I bought my 2” direct from the US. Good service but no advantage with the duties they slap on. Better to use Okularum.

With regard to duties, an (unrelated) case in point was the Burgess 10mm Supermono I bought. Very interesting eyepiece and excellent on axis. Good value at the point of sale but, crikey, by the time Her Majesty’s Customs and Excise and HMRC had done their bit ... 🤨. 

So start petitioning your government to match the US's $800 personal exemption amount.  If you're going to leave the EU, you may as well cozy up to the US with some bilateral trade agreements.  How is it fair to US retailers that it is often cheaper for US buyers to buy astro goods from UK dealers but not the other way around?  That, and forgo VAT taxation on imports if the foreign sellers have no business nexus in the UK to match US state sales tax rules.

I would think this had to have occurred in the factory prior to mounting the mirror to the holder.  It's speaks volumes to Chinese quality control that the mirror wasn't rejected during inspection.

Generally, the central 50% may be indistinguishable except on challenging objects like planets, globular clusters right at the verge of resolution, unequal doubles, and close doubles.  It's the outer 50% that differs markedly between pretty much all zooms and premium primes, especially in fast scopes.  Even at f8.3, I would imagine the zoom's outer part at 8mm should be easily bested by the 8mm Starguider.  At 24mm on the zoom, the view is so narrow that there isn't likely all that much outer field degradation.  You're also limited by the chromatic aberrations of the achro to some extent.  No eyepiece is going to correct that.

If you ever move up to a fast APO or really fast reflector and spring for premium widefields like Pentax XWs, Delos, Ethos, etc., you will be astonished at the difference in the views between them and an f8.3 achro with a Starguider 8-24 zoom.  The images are very sharp across the field revealing dimmer stars that are blurred out by lesser optics, the apparent fields of view are satisfyingly wider, and polish/coatings/baffling is so much better leading to darker backgrounds, better stray light control, and less scatter around bright objects.

1 hour ago, BernardH said:

Guys Thank you very much, I've learnt a lot!!! so now the second part of my question - which Porsche!!!!

Sorry, can't help you.  More of  a Corvette mid-life crisis kind of guy.  It's an American thing.

Looks like KUO may be making the APF UFF line based on the marked similarities between this updated 28mm UWA and the 24mm UFF.

That's just the nature of the beast due to the center edge to flip left for right.  Just avoid viewing bright point sources at night with it.  Use a planar diagonal instead of those objects.

Try a one or two step step stool.

No, this would be a toy telescope.  I actually bought one for $25 a few months back.  It comes with non-standard fittings (looks like 0.965", but it's not), a wobbly table-top tripod, super long barlows, two 30mm aperture stops, one behind the 70mm achromat and one midway down the focuser tube, and Huygens eyepieces.  I bought it for the 70mm achromat and metal tube that are actually pretty decent.  From that, I've been adapting it to a 2" diagonal finder.

There is nothing wrong with aluminum legs when done properly.  I really like using the Manfrotto 058B tripod under my DSV-2B mount for alt-az.

3 hours ago, Don Pensack said:

Looks like Meade did it for you: the 26mm MWA is around 90° and very inexpensive.

I've been eyeing it.  Given Meade's bankruptcy, I was waiting to see if there's a fire sale at some point.

7 hours ago, ollypenrice said:

Maks used to be significantly more expensive than SCTs. The good news with SCTs is that they are freely available on the used market and hold their value badly, making them a good buy.

Olly

I was tempted to pick up a 20 year old 10" Meade LX200 off Craigslist locally for $400 about 5 years ago.  A friend had given it to the guy, and he had no interest in it at all.  I just couldn't figure out where I would store it.

Either an extension tube or switch to a 2" diagonal.

2 hours ago, johninderby said:

Did a head to head visual comparison between a C6 and 150 mak and really couldn’t tell the difference on planets. Contrast was similar. Big advantage of the C6 was it’s weight. 

Reminds of a review done years ago:

Which is Best - Refractor, Reflector, or Catadioptric?

I wonder how a C6 and 150 Mak would have compared in that shootout.

You can always build an equatorial platform as described in this thread to add tracking to any Dob for an hour at a time.  The OP of that thread has a nice pdf describing his build.