Louis D

23 hours ago, johninderby said:

The focuser on the Bresser is a very nice CNC 2.5” R&P one and a lot better than the one on the 72ED.  However the 72ED is a proper APO and a very nice little scope.

With the optional dual speed knob.

Getting off-topic (sorry OP and mods)

Indeed, yours looks similar to the one on my TS-Optics FPL-53 triplet 90mm APO minus the camera angle adjuster.  However, the one in the Bresser description and the CN review describe it as single speed with plastic wheels:

Did you mod those features with aftermarket parts?

You're right, though, that 2.5" focuser is nicer than the 2" AT72ED focuser in that it doesn't slip because it is a R&P focuser:

Otherwise, they're very similar in smoothness and resistance to tilt.

I have similar Arcturus binoviewers that I have to keep the diopter adjusters tightened all the way down to avoid wobble and decollimation.  I also have to push undercut eyepieces tightly into the collets while tightening them down to avoid them tilting in their holders.  If I spin the diopter adjusters upward, I can watch the image in that eyepiece decollimate and trace a circle back to its starting position once it's been rotated 360 degrees.

Maybe you'll get a mechanically better unit with an exchange, but I would temper my expectations.  These binoviewers cost 1/3 to 1/4 what the Maxbrights cost, so it may not be reasonable to expect the same level of mechanical perfection in both.

6 hours ago, Barry-W-Fenner said:

I think I will check out & have a read up about the options above that @Louis D has kindly recommended to replace my 18mm BST.

The problem you'll run into around 18mm to 20mm is it's a no man's land when it comes to wide field and long eye relief in large part if you avoid the various 17mm offerings (Morpheus, ES-92, and .  There's the 20mm Pentax XW with field curvature that can be an issue for folks with presbyopia (bifocal wearers), the 22mm Vixen LVW which has long been discontinued but otherwise excellent at 65 degrees, the 22mm Nagler T4 which is expensive and a bit tight on eye relief, the above mentioned 18mm and 20mm UWAs which all have very limited eye relief, and the 22mm Astro Tech AF70 which is also known as the Celestron Ultima LX, Olivon 70, Omegon Redline SW, Skywatcher 22mm SWA-70, and several other brandings.  It is very comfortable with eyeglasses, flat of field, and sharp out to 90%+ of the field at f/6 with a true 70 degree field.

You might want to get a 3.2mm to 4mm eyepiece for nights of exceptional seeing.  I haven't tried the 3.2mm Starguider, but the 3.5mm Pentax XW is very nice.

If you have the money, I'd go for a 17mm ES-92 to replace the 18mm Starguider and a future 18mm to 20mm UWA like a 20mm Nagler T2/T5, 20mm Meade UWA, or 18mm ES-82.  The ES-92 eye relief is very generous, the contrast if phenomenal, and edge correction is excellent.

2 hours ago, Charlie 2436 said:

I am going for the Altair Astro 30mm Ultra-Flat which I believe  is the same as the APM 30mm Ultra-Flat for wide field.

Optically the same, but with a stainless steel barrel making it heavier than the APM version.

3 hours ago, Charlie 2436 said:

My problem is which other one to go for , either the Morpheus 17.5mm , 12.5mm or 9mm ,or the APM 12mm HI-FW .

I would lean toward the 12.5mm.  I've found I like observing around 75x quite a lot with the aperture you're using because it yields a near optimal 2mm exit pupil.

As for Morpheus vs. APM, I'd probably lean toward the Morpheus since from what I've read, it has more comfortable eye relief for eyeglass wearers and slightly better edge correction.  The APM seems to excel at central contrast and resolution like the 12.5mm Docter/Noblex it tries to emulate.

2 hours ago, LondonSi72 said:

Thank you Louis.  I'll have a look for a long barlow and see if that does the trick.  They seem to be harder to find these days, as I guess the optical quality of short barlows has improved, and they're more convenient.  (I'm still intrigued as to how you can determine where a particular eyepiece / barlow combination would need to be in the focuser for it to focus)

You can't even use long focus Barlows in a refractor's diagonal because they require more in-focus than most of them have to spare.  The difference is that a Newtonian focuser essentially has no bottom (at least until you hit the secondary) while a refractor's diagonal only has about room to accept the first 1.5" of a barlow before bottoming out on a hard stop or hitting the diagonal's mirror/prism in a 2" unit.  Thus, you can just keep inserting the Barlow in the Newtonian focuser until it comes to focus which is usually before you contact the shoulder.  This can be 2" to 3" or more.  This just isn't an option in a diagonal, thus the popularity of shorty Barlows which can be used in either.

12 hours ago, John said:

One of these perhaps ?:

https://www.bresser.de/en/Astronomy/BRESSER-Messier-AR-102xs-460-Hexafoc-Optical-Tube.html

 

Yes, not sold in the US, so not familiar with it at all.  I think I'll stick with my AT72ED for widest field scanning of the skies.  I don't think I'd want to trade off excellent color correction, two speed focuser, and all metal construction for an additional 30mm of aperture, though.  It would be intriguing if they went with an FPL-53 triplet to bring down the false color to at least ED levels.  Of course, the price would be at least $1000 higher.

After reading the review's mention of field curvature, I'd have to recommend budgeting for a TSFLAT2 to flatten the field if you're going to use it for widest field scanning of the skies.  I use one with my 432mm FL 72ED to good effect.  Screwing it onto the front of the rather long 2" diagonal insertion tube of my 2" GSO 99% dielectric diagonal resulted in slight overcorrection, causing field curvature of the opposite sign.  Since that diagonal has SCT threads, I replaced the nosepiece with a 15mm SCT to M48 adapter tube and thread the TSFLAT onto the end of it.  The resultant field is just about perfectly flattened.

47 minutes ago, John said:

One of these perhaps ?:

https://www.bresser.de/en/Astronomy/BRESSER-Messier-AR-102xs-460-Hexafoc-Optical-Tube.html

 

Rather confusingly it claims "Richfield telescope with ED glass lens" and is also an "Achromatic Refractor".  If it has a 4" ED lens for that price, I'd be very impressed.

I wonder at low powers how much violet fringing would be visible.  I also wonder how well spherical aberration is corrected.  I'm just trying to figure out if it might work well enough with a 35mm Aero ED if there's all sorts of other aberrations to deal with.  The outer 25% of the field would be a bit fuzzy with it, but if there's a bunch of other stuff going on out there, it might not seem so bad.  It would definitely come close to maxing out the TFOV possible.

What refractor are you using that's a 100mm f4.6?  Either it's an exotic ED/APO (Borg/Pentax?) or it's an achromat that has loads of color fringing.

The problem at f4.6 is trying to keep the exit pupil below 7mm.  A 7*4.6=~32mm would be your max usable eyepiece focal length to possibly make full use of your available aperture.  Another problem is finding an eyepiece that can handle the steep light cone.  I agree that the 30mm APM UFF would probably be a good bet for you.  However, you're only going to get about 4.7 degrees TFOV, a bit shy of the 5 degrees you desire.

I'm glad someone got some use out of this old thread.  @Pawel only posted once and hasn't even visited since that first day he/she joined and posted, so didn't even ever read all the responses.

One problem, the 40mm Aero ED has been sold out worldwide for several years now.  There's been no sign of new production.  The 35mm Aero ED is nearly as wide, TFOV-wise, and wider AFOV-wise.  Correction isn't quite as good, but it's not bad compared to some other offerings in this price range.  Eye relief is a bit tight on it because the eye lens is recessed 7mm for no apparent reason.  It is nice and light, so it won't throw off your scope's balance.

The 40mm ES-62 is basically the same as the 40mm Meade 5000 Plossl.  It's great in the inner 50%, and then gets worse toward the edge.  However, it lacks much distortion, so the moon stays nice and round as it moves across the field.  Eye relief was great on the Meade and will probably be very good on the ES-62 as well.

Here's a comparison image of a bunch of my widest field eyepieces taken through a field flattened 72ED refractor:

I generally only clean when I notice bright objects noticeably blurring as they move across the field of view.  I then back away and try to identify the culprit which is usually a smudge or eyelash goo.

From 25585's reports on CN, the Orion LHD line sounds pretty similar to the Nagler T4 line in that both lines have 30mm eye lenses, some minor SAEP, and a need to push in tight with eyeglasses to see the entire field.

I had forgot about the APM 84.  I'd be tempted to get one if I wasn't so pleased with the 12mm ES-92.

The Meade MWA line is actually more of an 82 to 84 degree line with prominent SAEP, so they're also an option in some of the focal lengths having longer eye relief.

1 hour ago, Charlie 2436 said:

Thanks for the advice Michael. I guess I would be better going for the 9-27mm version, although the 7.2-21.5mm Would have suited me better.

While on the subject of eye relief does anyone know of any 82 degree eyepieces with good eye relief that don’t cost a small fortune.

The only 82 degree eyepieces that I've found I can use comfortably with eyeglasses are the 22mm Nagler T4 and the original 30mm ES-82 with the mushroom top.  It was identical to the 30mm Meade 5000 UWA and 31mm Celestron Axiom LX if you can find them used.  Alternatively, the Morpheus have 78 degree measured AFOVs, so very close to 82/84 degrees.  Many of the affordable "82 degree" eyepieces are actually 78 to 81 degrees once measured, so take marketing claims with a grain of salt.

The ES-92 line is very comfortable with eyeglasses, but big and expensive.

2 hours ago, Charlie 2436 said:

Hi All

I am looking into getting the ovl hyperflex zoom as I have read such good things about it. My problem is eye relief the 7.2-21.5mm has 15mm of eye relief, I wear glasses and was wondering if it was ok for glasses users or would I be better going for the 9-27mm version which has 18mm of eye relief. 
Thanks Robert 

I have the Surplus Shed version, and I've measured the usable eye relief to be between 9mm and 11mm.  It is not really usable at all with eyeglasses unless you have a tracking mount to keep small objects centered.  However, if you Barlow it, the exit pupil may become small enough that you won't need eyeglasses to correct your eye's astigmatism.  The eye lens is very small (16mm diameter on mine) and recessed, so don't expect big eye relief.

I like the Celestron (Olivon) Regal zoom which I've measured to have 13mm to 16mm of usable eye relief, although it certainly feels longer than that in use, especially with the eye cup screwed all the way off.  The only problem is locating these zooms.  They are generally only sold with spotting scopes.  It does not have filter threads, so there is that.

On 03/09/2020 at 06:02, juda222000 said:

Thanks all, So maybe I need to change the telescope I'm going to get? I mean I'm 6ft tall lol and both my 5 year olds are 4 ft, I would have to carry a table around with me to put this on so me and my kids could look through this.

Not really following your line of reasoning on why you'd want to put the scope on a table.  You might want a table to put your star charts and eyepieces on, but not the telescope.  You will probably want to buy a stool or observing chair, though:

Standing to observe is not comfortable in the long term:

Here's the proper use of a table for astronomy:

There are plenty of fold-up/roll-up tables for camping if bulkiness is a concern:

And if the scope is still too low, put it on a stand of some sort:

I went with a large and deep Pelican-style case so I could store my eyepieces upright.  It allows many more eyepieces in a single case.  One downside is I have to have the layout memorized since many eyepieces look the same from the top in the dark.  Another is it allows for the weight to creep as I've added more heavy eyepieces.  The case is over 20 pounds now.

Look for an older, long Barlow.  They usually require a fair amount of out focus rather than in focus.  My favorite very long Barlow is the 1.25" Orion Fully Baffled 2x made in Japan in the 90s.  Side by side testing on the Trapezium showed it is slightly sharper than my Tele Vue 1.25" 2x and Meade 140 2x, both of which are phenomenally sharp and mid-length Barlows.  The Orion is about 6 inches long and focuses about 2 inches out, IIRC.  I just don't insert it all the way into the focuser rather than crank the focuser that far out.

Why cellphone cameras are so handy to have today.  Someone is always snapping an image of a whiteboard in a conference room after a productive brainstorming session at work.

35 minutes ago, Alan64 said:

My Orion 6" f/5 Newtonian("StarBlast 6") and the "XT6 Dobsonian" have always sported 1.25" plastic focussers.  My own 6" is from 2012.  Now, back in the day when Gieseler still owned Orion, who knows.

Guess I never caught that difference relative to the 8" and the Sky Watcher version.

17 hours ago, Charlie 2436 said:

Does anyone know if the Altair Astro 30mm Ultra Flat is the same eyepiece as the APM 30mm ultra flat field , except that it’s Green . 

I've read it's optically the same, but heavier due to a stainless steel instead of aluminum barrel.

2 hours ago, Alan64 said:

The Orion 6" has a plastic 1.25" focusser

When did that happen?  Didn't the Orion 6" used to have a 2" focuser just like the Synta made Sky Watchers?

Assuming  you're in the US, check the classifieds on cloudynights.com as well as Craigslist for your local area for used deals.  Big Dobs don't ship well (expensive and bulky), so checking locally helps a great deal.  Check nearby cities as well if you're willing to meet half-way.

As far as scopes go, it's hard to beat the 6" floor standing Dob for all around versatility and image quality for around $300 new.  Expect to pay no more than $200 for a used one in good condition.  Right now, the new ones are all on back order everywhere, so you have time to save up.  Get on a waiting list until then.  I recommend Astronomics, Agena Astro, OPT, HPS, and Orion.  They are all knowledgeable and can help you make informed decisions and stand behind their products.

As Mike at Astronomics recently said in his mailing list as pertains to constrained product supply:

Due to unexpected demand in astronomy products from a stay at home pandemic, rocket launches, and a very bright comet all manufacturers are stuck in an awkward position that nobody could have predicted.  We appreciate your interest and your understanding in the matter as we are filling orders as fast as products can come in.  Astronomy is a hobby about patience, so please have a little with us currently.  Thank you. 

As long as they get progressively worse from center to edge as you move a bright star from center to edge, it's the eyepiece causing these issues.  The eyepieces are probably simple designs from the past intended for f/10 to f/15 or slower scopes.