Louis D

2 hours ago, Don Pensack said:

Louis,

I notice the right side of each image is in better focus than the left edge.  Is your scope's objective tilted relative to the target?

It's often related to how well I can center and level the camera relative to the eyepiece.  Remember, I'm doing this by hand, taking several shots, and selecting the best for release.

24 minutes ago, bomberbaz said:

@Louis D  27 and 28 both 100 FOV appear to be more like a tele extender arrangement rather than barlow but I get they are using a barlowing effect to improve the FOV. Very clever arrangements and no wonder they are so expensive. 

Substitute negative focal length group for Barlow to make the statement more generic.  Even tele extender/magnifiers use an initial negative focal length group.

Notice that even in positive only designs like 19 (Panoptic-like), a negative power element is used for the field element to improve field correction.

On 13/11/2021 at 14:02, bomberbaz said:

So the wide field EP's with the 100+ fov are likely barlowed already to help achieve this @Peter Drew

Notice in the following eyepiece raytrace diagrams that the field lens group (small diameter group on the right in each diagram) in pretty much all of the UWA and HWA eyepieces (diagrams 20 through 28) diverges the incoming rays just like a Barlow:

On 14/11/2021 at 12:21, Richard N said:

The results are in. The comparison was between a Starguider ED 18mm + Astro Essentials 2x Barlow and an Svbony 68 uw 9mm (red bands). And (drum roll...) the difference was... 

...nothing. I have spent a while swaping them on various stars and there is no dicernable difference. The faintest stars were just visible on both eyepieces.  However, I'm likely to keep the Svbony 9mm as it's a lot smaller, lighter and less cumberson than the combo. I did expect to see some difference but even with full imagination engaged I have admitted defeat. Maybe I'm looking at the wrong characteristics? I will try them on some doubles next.

Try them during the daytime to see if SAEP (kidney-beaning) is more of an issue with one than the other.  I've repeatedly read that the 9mm UWA (at least the older gold band version) has strong SAEP that becomes obtrusive with small entrance (iris) pupils.  This can happen during white light solar observing, lunar observing near full moon, and daytime spotting scope usage.  It's the main reason I've never bought the 6mm and 9mm UWAs despite their low price, wide field, decent eye relief, and good field correction because I'm hyper sensitive to SAEP.

Alternatively, I've found that some shorty Barlows can induce SAEP in some longer focal length eyepieces, so the 18mm+Barlow combo might also exhibit SAEP.

11 hours ago, FLO said:

Unfortunately Bresser's EU distributor in Germany (Astroshop & FLO source Bresser scopes from the same distributor) say the Messier Dobsonian series will be unavailable for some time. 

This morning they say: 

Bresser Messier Planetary 6" Dobsonian:  April 2022

Bresser Messier 8" Dobsonian:  Feb 2022

Bresser Messier 10" Dobsonian:  Feb 2022

HTH, 

Steve 

Appears to also be out of stock across the US (as the Explore FirstLight) as well. ☹️

On 14/11/2021 at 01:12, Roog said:

The skywatcher finder fine though it was has an un protected plastic edge which has put some nasty dinks in my new and very expensive spectacles, thankfully the marks lie out side of my main view

Online order a pair of single vision distance glasses with the lowest index plastic possible and use them strictly for astronomy.  The advantages are that the entire field will be in focus at once, off axis chromatic aberration will be minimized (higher index lenses have higher dispersion or prismatic effect), cost of the glasses will be minimized (the higher the lens index, the higher the cost), the lenses won't develop microscratches from daily wear that become visible at high power with tiny exit pupils, and if you do manage to ruin them, they won't be expensive to replace (my pair was under $20 from EyeBuyDirect a few years ago).  The downsides can be thicker, heavier lenses because of the low index and lack of close vision for bifocal wearers.

I don't know about UK laws, but in the US, your optometrist must provide you with a copy of your vision prescription when asked; and it is perfectly legal to order prescription glasses from online vendors.  I've found the frames and lenses to be just as good as those sold by my optometrist.  In fact, I've had several of the latter's frames fail within a year while none of my online frames have had any issues.

Going to a 2" visual back and 40mm SWA eyepiece easily overcomes the increase in focal length to get to a wider field of view with a Synta 127 Mak with about 40% vignetting near the edge.

I'll second the Night Sky Planisphere recommendation.  I've had mine for 23 years, and it has held up very well.  Here are recent scans of the front (north) and back (south) sides of my large plastic version for 20°-30°N latitude:

7 hours ago, johninderby said:

If you need room there is allways……😁

https://www.americancarcentre.com/product/all-new-chevrolet-suburban-7-8-seat-luxury-suv/

Yep, my father-in-law downsized to a Chevy Suburban a couple of decades ago from a full size 1990s Chevy Van like the one below after empty nesting.  He absolutely loves it.

Suburbans are referred to as Texas station wagons (estate cars) around here.  However, full sized pickups are more popular due to their utility.

7 hours ago, DhamR said:

Equinox would be a pretty big car by UK standards!

Interesting, they're considered a compact SUV by Texas standards.

1 hour ago, bosun21 said:

The only load I put on my Dobsonian focuser is the eyepiece as it’s a strictly visual affair. If I was selecting a telescope for astrophotography then I would go for the R&P design. It’s the old saying “ Horses for courses “. 

Are you implying I was loading my AT72ED with photographic gear?  I'm not sure, but it sort of sounds that way.  I'm just loading it with a 2" Dielectric diagonal and 17mm ES-92 or 1.25" diagonal and binoviewer with two eyepieces to exceed 2 pounds in a hurry.

It's all but impossible to make a focuser slip on a Dob because it never comes close to being in a vertical orientation, so that's a non-issue even for astrophotography with one on an equatorial platform.

The only gripe I've got with a smooth rack "Crayford" focuser is with the one on my AstroTech 72ED.  It slips horribly near zenith with any load over two pounds (~1kg).  If I tighten down the tension as much as I dare, it won't slip, but it also can't raise the load without me putting my thumb under the diagonal to coax it upward.  By comparison, the 2.5" R&P focuser on my TS Optics 90mm APO has none of these issues.

I know that the MoonLite and Feather Touch focusers don't have these lift issues despite not having a geared rack, so it's just a matter of having a well executed, quality design.

I do have an original style R&P focuser on my 1990s era 15" Dob that wobbles horribly, so just having a geared rack does not guarantee a quality motion.

23 minutes ago, bosun21 said:

Was it the Baader 2” click lock that you fitted?. I was looking at doing the same thing however I thought that it was only the 1.25” that fitted due to the diagonal being 1.25”

I'm guessing this adapter was added to the back of the Mak to bring it up to SCT thread size for the BCL.

1 hour ago, PeterC65 said:

That's a nice idea but I've swapped the visual back on my 127 for a 2" Clicklock clamp which leaves too little space between the focus knob and the clamp for a bigger focus knob. I made this swap as I'm forever canting over the diagonal to get just the right observing position for the eyepiece and so wanted an easy to adjust clamp. I thought that going for a 2" would give me room for flexibility in the future (if I ever decide to get a 2" diagonal for example).

Anyway, I've made a clothes peg instead, just re-using the spring.

I've not had a chance to try it out yet but I'm hoping that fingertip nudges at the far end of the peg will allow fine focusing without vibrating the scope.

Try putting a foam grip for handlebars or foam tape over the end of the peg.  I've found it helps dampen the contact shock from your fingertip as you search for best focus.  Check Amazon and/or ebay for ideas.

2 hours ago, johninderby said:

They were bought by Orion USA and are now a seperate division of Orion and will continue to trade as Meade.

 

Not quite accurate.  Meade was failing financially when it was bought by Ningbo Sunny in 2013.  As a result of an antitrust lawsuit against NS (and several other companies that settled before trial) brought by Orion USA for suppressing competition and conspiring to fix the prices of consumer telescopes in the U.S., NS lost and then was found to be acting in bad faith (transferring cash out of the country to avoid paying the settlement when explicitly ordered not to, etc.).  NS then had Meade declare Chapter 11 bankruptcy to avoid paying the settlement amount.  To partially recover the amount of the court ordered settlement ($16.8 million), the Meade brand was awarded to Orion USA by the courts.

Orion USA owns the Meade brand, but never actually bought it.

I have no idea which Chinese/Taiwanese optical firm Orion is contracting with to manufacture Meade SCTs now.

The Hyperion line is more or less a lower cost, Chinese interpretation of the Japanese Vixen LVW eyepieces.  A comparison by our own @John of the two lines can be read here.

Both lines, along with the Pentax XL/XW, Baader Morpheus, Tele Vue Delos, Omegon Redline, and several other lines, use a two stage eyepiece design.  First, they all use a long focal length, positive upper section that forms the image seen by the eye.  It has both long eye relief and a 65 to 76 degree apparent field of view.  Second, they all use a negative lower section similar to a Barlow or Smyth lens that magnifies the incoming image for presentation to the upper section.  The larger upper section remains relatively unchanged across focal lengths, decreasing manufacturing costs while maintaining a similar viewing experience through each variation.  It is the lower, negative section that varies wildly from focal length to focal length.  Some of the most advanced designs actually use an intermediate lens group between the two sections to further refine the image correction.

Here's a diagram of the older Pentax XL line:

Ignore the XL40 design, it was a unique 2" design.

Here are two diagrams of the Pentax XW line:

Again, ignore the XW30 and XW40 designs as they are unique 2" designs.  Even then, it's clear the 30mm has a weak negative section feeding a near copy of the 40's positive section.

Take note of how similar the 1.25" eyepiece positive sections (the bigger ones on the right in each diagram made up of four lenses in 3 groups) are across all focal lengths.  Only the 20mm/21mm/28mm versions vary a bit in the field (left-most) lens of the positive group.  The other two groups remain basically unchanged, keeping down manufacturing costs.

Now notice how wildly different each negative section (the smaller ones on the left in each diagram) vary from focal length to focal length.  The shortest focal lengths actually split it into two groups to create what appears to be a telecentric magnifier like a Tele Vue Powermate (left-most group magnifies by divergence, right-most group brings the light bundle back together again, but at higher power).  This allows for high magnification without sending wildly diverging beams into the positive section.  Wildly diverging incoming beams can cause vignetting and eye relief extension, among other issues.

Also notice how the 7mm, 10mm, and 14mm XW versions each have an intermediate lens group not found in the earlier XL designs.  I believe they were added to improve field correction in going from 65 degrees for the XL line to 70 degrees for the XW line.

The upshot of all this is that to maintain long eye relief and wide field of view requires a large positive section with a somewhat distant negative section feeding it a magnified view.  This results in a rather large eyepiece as you discovered.

On 06/05/2020 at 17:06, RobertI said:

Just did some UK/US price comparisons, and interestingly in the US, Maks are more expensive than their SCT equivalents, in the UK the reverse seems to be true.  Not quite sure what conclusions to draw (it's late!). 

• Celestron C8 - £1067 in UK, $999 in US
• SW MAK 180 - £805 in UK, $1200 in US
• Celestron C6 - £649 in UK, $599 in US
• SW MAK 150 - £485 in UK, $750 in US

A bit late to reread this post, but did you remember to subtract VAT from the UK prices before comparing them to US prices?  As I've repeated many times, US sales tax varies from state to state, county to county, and city to city.  As a result, it cannot be included in the listed sales price online.

I have no idea how local governments collect their VAT.  Do they get a fixed cut of the national VAT on every sale?

I'm a bit confused.  The Celestron 130 doesn't appear to be that big of a scope relative to something like a solid tube 8" Dobsonian.  How small of a car do you drive to Scotland?  How much other luggage goes with you to Scotland?  My daughter takes her Chevy Equinox camping.  It has plenty of room for her, her fiance, her dog, their camping gear, their clothing, a 127 Mak, tripod, and alt-az mount.  It's considered a rather compact SUV by American standards (as compared to a Chevy Traverse or Suburban).  I take my old Chevy Astro van camping, and I can pack my 15" truss Dob in back fully collapsed with plenty of room to spare for gear for the entire family with the third seat removed.

It would help to understand exactly how you're getting to Scotland, and how much space you have to spare before making travel scope recommendations.

3 hours ago, PeterC65 said:

The wife tells me that these EPs are to be wrapped up for Christmas!

What?  You told the wife you're getting these?  I usually until I've had the chance the use them a few nights to ensure I want to keep them.  Then, when she asks what I want for Christmas, I tell her I'm already taken care of, and she can wrap them up at that point.  She's usually thrilled to be done so easily with shopping for me.

Try putting some vibration dampening pads under each tripod foot.  I found that vibration dampening went from 2 to 3 seconds down to a half second with them.  This was with my rather solid DSV-1 mount on a Manfrotto tripod and a 72ED scope.

I agree with @scotty38.  I'd take my 17mm ES-92 Barlowed to 8.5mm any day over my generic 9mm Kellner.

On 10/11/2021 at 15:55, Pixies said:

Yep - dobby.

🤔 

5 hours ago, Ricochet said:

F6. From what I recall, only the central 1/3 was useable. 

Was it a flat field scope?  I've noticed field curvature in short f/6 refractors rather quickly ruins the field; thus, I use a TSFLAT2 with my 72ED.

If it was an 8" f/6 Dob, then it can basically be treated as flat field.  I'm sorry it didn't work out for you either way.

4 hours ago, bosun21 said:

Thanks for your reply and was thinking about using in my 127 Maksutov. I have just bought a Baader Hyperion Zoom and the Baader Barlow with a 32mm Celestron Omni for finding targets. I have also bought several BST Starguider eyepieces. I don’t think that the SVbony 68’s deserve the stigma attached to them.

Here's how the 20mm SVBONY UWA looks in my 127 Mak from the same distance as the above comparison image:

I included the Orion Centering SWA for comparison because it performs more poorly at both f/6 and f/12.  It is a bit wider, but notice that the edge marks are less distinct.  To my eye, the SVBONY looked fine at f/12 while the Orion did not.

This is more what is likely to happen in the US.  They redesign a 90 degree intersection into a "roundabout" by putting a raised, circular island in the middle of it.  Next thing you know, some drunk comes tearing down the street late at night and hits the raised island, launching it through the air:

I was most impressed it dislodged the large boulder.

3 hours ago, Mr Spock said:

Indeed, Americans seem to confuse 'traffic circles' with roundabouts. The two are completely different. We've already seen that confusion here.

Pretty much, all American "traffic circles" are roundabouts in reality.  The old fashioned traffic circles like Columbus Circle are all but nonexistent nowadays.