Eyepieces for a (olds) Edmund Astroscan - Plossl or Ortho...or?

[Travelman]

Hi SGL´ers

I am the happy owner of an Edmund Astroscan and need some advice on eyepiece (in the 18-26 mm rance

a) It is an 105mm f/4.45

b) Despite being properly colimated, is would be a understatement to say that stars are pinpoint at the outer 20% of the field.

c) Being a ball-mounted telescope, I can forget about a Paracorr or similar, it will sag

d) For same reason - sagging - any eyepiece shouldn´t weigh more than 100 gr.....

 

This obviously limit my choices....I am aware that conventional wisdom would be to go for a Plossl, but my thinking is that e.g an 18 mm Ortho from Baader might be a better choice. My resoning is that altough it has an apparent filed of view of only 52 degree, ,I am basically only loosing the outer far of the field (which isn´t a great loss)

Am I out of my mind?

Any other alternatives

 

All kind of feedback would be greatly appreciated!

 

Torben Ask

Copenhagen, Denmark

[NGC 1502]

Late reply here……

I’ve had an AstroScan for around 10 years and love it to bits😊

They were designed as a no hassle wide field low to medium power telescope. Originally they came with a 28mm RKE eyepiece for 16x and 3 degree field. If the collimation was reasonably ok then up to around 50 to 80x was good, that’s how mine is.  However, 16x does produce a large exit pupil, not ideal.

You have correctly mentioned that heavy eyepieces will cause the scope to sag down. An ideal but very expensive eyepiece would be a TeleVue 19mm Panoptic for 23x, almost 3 degree field and a 4.5mm exit pupil. But the 19mm Panoptic doesn’t have glasses friendly eyerelief.  The 18.3 DeLite would be a brilliant alternative. Big snag here is the high prices even second hand. I use an 18mm TV Radian for 25x, well over 2 degree field, a very acceptable 20mm eyerelief with 4.2mm exit pupil.

For many premium eyepieces are out of the question, if that’s where you are then compromises are necessary. Perhaps something from Explore Scientific or StellaLyra from our sponsors FLO, take a look at their eyepiece section, or the private adverts on this forum.

You have mentioned an 18mm Ortho. That’s 25x and a 2 degree field, a very acceptable place to be😊

There’s loads of AstroScan info on Cloudy Nights forum to keep you reading all night. But if it’s a clear night don’t do that, go out and enjoy the view😊

Cheers from Ed.

Edit-  I’ve just checked FLO eyepiece section.  The 18mm StellaLyra UFF looks brilliant….if the price is acceptable to you…..recommended😊

 

Edited August 27 by NGC 1502

[Don Pensack]

I second the 18mm UFF recommendation.  Very sharp, lightweight, and enough eye relief for glasses (for most people).

[Travelman]

Thanks @Don Pensack  and @NGC 1502

 

Indeed the 18mm StellaLyra UFF is interesting, but the weight is +200 grams - too heavy for the Astroscan.

 

What are your thoughts about the following from Teleskop Service:

TS-Optics 25 mm Premium Flat Field Eyepiece

https://www.teleskop-express.de/en/telescope-accessories-5/eyepieces-295/eyepieces-1-25-inch-with-big-field-70/ts-optics-25-mm-premium-flat-field-eyepiece-1-25-60-field-1-25-inch-15928

or :

TS-Optics 19 mm Premium Flat Field Eyepiece

https://www.teleskop-express.de/en/telescope-accessories-5/eyepieces-295/eyepieces-1-25-inch-with-big-field-70/ts-optics-19-mm-premium-flat-field-eyepiece-1-25-60-field-1-25-inch-15927

 

Kindest

 

Torben

[Louis D]

Those are the same as the Astro-Tech PF line.  Lots of reports on CN that they do best at f/12 and above.  They would probably be a mess in the outer 50% of the field at f/4.45.  You might as well stick with Plossls at that point.

[NGC 1502]

5 hours ago, Travelman said:

Thanks @Don Pensack  and @NGC 1502

 

Indeed the 18mm StellaLyra UFF is interesting, but the weight is +200 grams - too heavy for the Astroscan.

 

My own AstroScan is fine with an eyepiece of that weight. The weight has to be significantly higher to cause the scope to sag down.  One issue that could cause excessive sagging is the state of the 3 felt pads on the supplied base. If they are old, compressed and polished by much use, that could well restrict eyepiece choice unnecessarily.

Many DIY stores or even “Poundland” type budget stores sell suitable felt padding. Sometimes sold as stickers to prevent damage to surfaces like coffee tables or similar.  Experiment is necessary to get the right level of friction. You can live with a less than ideal friction because the AstroScan was never intended as a high power instrument where silky smooth movements help.

My own example is the least hassle quick look telescope I own. The collimation is good enough for sharp views up to around 80x. If you’re satisfied with a tiny Saturn it’s even good for that. I have tried it on the double-double near to Vega, a bit blurry above 100x but the 4 components can be discerned. Not a great view but then that’s using the AstroScan beyond the intended use.

As already said, I love mine to bits😊

Torben…..hope you enjoy yours👍

Best from Ed in the UK….

 

 

[NGC 1502]

4 hours ago, Louis D said:

Those are the same as the Astro-Tech PF line.  Lots of reports on CN that they do best at f/12 and above.  They would probably be a mess in the outer 50% of the field at f/4.45.  You might as well stick with Plossls at that point.

Good call. An 18mm (or close to that) Plossl, or regular Ortho would work well. 25x with 2 degree field is, in my opinion, better than the 16x 3 degree field that the original 28mm RKE produced. That’s because under our mainly light polluted skies, a very large exit pupil gives a washed out view. 25x is noticeably more contrasty with a darker sky background. 

[Mr Spock]

What about the Ursa Major flat field 19mm 65°? No weight listed but it does look fairly compact and light. https://www.firstlightoptics.com/ursa-major-eyepieces/ursa-major-fmc-flatfield-eyepiece-19mm.html

[John]

6 minutes ago, Mr Spock said:

What about the Ursa Major flat field 19mm 65°? No weight listed but it does look fairly compact and light. https://www.firstlightoptics.com/ursa-major-eyepieces/ursa-major-fmc-flatfield-eyepiece-19mm.html

The Ursa Major range seem good value for their price point. I was loaned a set by FLO recently and found them well made and pretty decent performers. As good as the Starguiders I reckon.

The 19mm is no larger or heavier than a plossl of similar focal length.

Edited August 30 by John

[Travelman]

14 hours ago, Louis D said:

Those are the same as the Astro-Tech PF line.  Lots of reports on CN that they do best at f/12 and above.  They would probably be a mess in the outer 50% of the field at f/4.45.  You might as well stick with Plossls at that point.

I just read up on that, based on your input - seems as if you have point :-)

[Travelman]

10 hours ago, NGC 1502 said:

My own AstroScan is fine with an eyepiece of that weight. The weight has to be significantly higher to cause the scope to sag down.  One issue that could cause excessive sagging is the state of the 3 felt pads on the supplied base. If they are old, compressed and polished by much use, that could well restrict eyepiece choice unnecessarily.

Many DIY stores or even “Poundland” type budget stores sell suitable felt padding. Sometimes sold as stickers to prevent damage to surfaces like coffee tables or similar.  Experiment is necessary to get the right level of friction. You can live with a less than ideal friction because the AstroScan was never intended as a high power instrument where silky smooth movements help.

My own example is the least hassle quick look telescope I own. The collimation is good enough for sharp views up to around 80x. If you’re satisfied with a tiny Saturn it’s even good for that. I have tried it on the double-double near to Vega, a bit blurry above 100x but the 4 components can be discerned. Not a great view but then that’s using the AstroScan beyond the intended use.

As already said, I love mine to bits😊

Torben…..hope you enjoy yours👍

Best from Ed in the UK….

 

 

Hi Ed - thanks a lot of your suggestions about experimenting with the felt.

 

Actually, that would be a no-brainer for me, as I happen to have 2 bases. Thus, I can use what I view as the best base/felt as a reference, and then experiment with the other.

My "challenge" is that I hads the Astroscan for in the US (@ Scientifics) for collimation, cleaning & service, 2 year ago. I then opted to get the Astroscan upgraded to the factory installed Red-Dot finder (although a far cry from e.g. Baader SkySurfer III, still dramatically better option than the Astroscan Peep sight), it did shift the balance slightly.

 

Further, I have now ordered a 3D printed drawtube that should save me some 40 grams AND give better traction against the rubber).

 

Once I recieve that, I can then test the new balance & estimate how heavier eyepiece I can ise now, compared to right now.

Adding to that the potential improvement after a hopefully succesfull experimentation, should then open up to a much larger number of potential eyepieces.

 

PS: The guy who 3D prints the drawtube, also makes front caps, dew shield, solar filten & finder, finder, replacement knobs, Bathinov masks and even a counter weight. I can provide you with his info , if needed. (I don´t want to risk being in breach any advertising rules here on SGL)

 

Kindest

 

Torben Ask

Copenhagen

[Travelman]

6 hours ago, Mr Spock said:

What about the Ursa Major flat field 19mm 65°? No weight listed but it does look fairly compact and light. https://www.firstlightoptics.com/ursa-major-eyepieces/ursa-major-fmc-flatfield-eyepiece-19mm.html

That looks like a real bargain!

 

Thanks for the tip

 

Torben

[NGC 1502]

Thanks Torben, PM’d for info😊

[Louis D]

10 hours ago, Mr Spock said:

What about the Ursa Major flat field 19mm 65°? No weight listed but it does look fairly compact and light. https://www.firstlightoptics.com/ursa-major-eyepieces/ursa-major-fmc-flatfield-eyepiece-19mm.html

Given the strong resemblance to the A-T PF and TS PFF lines, along with identical focal lengths (although FLO offers a couple more focal lengths), I'd say they're the same eyepieces under different house brands.  As such, reports/reviews about one line could safely be assumed to apply to the others.  Differences in specs between lines should be taken with a grain of salt unless the retailer did their own independent testing to arrive at their numbers.

[Mr Spock]

1 hour ago, Louis D said:

I'd say they're the same eyepieces under different house brands.

Um, no. FLO has already said they are a new eyepiece and if you look at the specs there are differences. For example the A-T 25mm is listed as four elements whereas the UM 25mm is five elements.

[Louis D]

4 hours ago, Mr Spock said:

Um, no. FLO has already said they are a new eyepiece and if you look at the specs there are differences. For example the A-T 25mm is listed as four elements whereas the UM 25mm is five elements.

I guess we'll just have to agree to disagree then that FLO commissioned an entirely different line of eyepieces from all the other house brands of KUO's (Sky Rover) new Premium Flat Field line.

[Don Pensack]

Correct.  They are the KUO Premium Flat Field line sold by: 

BTW, all the 25mm have 5 elements, though it's possible they all have 4 elements.  Until someone takes one apart, we won't know.  All the other focal lengths have 5 or 6 elements.

They are available in the EU under other labels (usually called Premium Flat Field):

Artesky

Lacerta

Tecnosky

Telescope Service

Omegon

 

And available elsewhere for low prices under the names:

Astrotech PF

Auriga

Sky Rover

Specs from the mfr:

Focal Length: 25mm
Eye Relief: 23mm
Exit diaphragm (diameter): 25.9mm
Optical Structure: 5 elements in 3 groups
Coating: Fully multi-coated (FMC)
Net Weight: 80g
Size: 73x35mm (width x height)
Interface Size: 1.25-inch interfaces, with standard 1.25-inch filter thread
Eye Cup: Folding

Edited August 31 by Don Pensack

[Don Pensack]

2 hours ago, Louis D said:

I guess we'll just have to agree to disagree then that FLO commissioned an entirely different line of eyepieces from all the other house brands of KUO's (Sky Rover) new Premium Flat Field line.

Well, it is a new brand name.

[Mr Spock]

As for reviews, I'll go with opinions from people I know and trust and who have actually looked through one...

Most of what I've read is speculation and guessing. Even down to the number of elements. I'm sure people here prefer facts rather than opinion.

[Don Pensack]

Well, companies that advertise element counts in eyepieces are sometimes wrong.

Astrotech advertises their 25mm Paradigm eyepiece as 6 elements, but it has been dismantled and there are only 5 elements.

Barsta's "Planetary" eyepieces were all advertised as having 6 elements, but the 25mm has 4 elements.

Pentax XWs vary from 6 to 8 elements.

Tele Vue Ethos vary from 8 to 10 elements.

It would be unusual for a line of eyepieces to have the same number of elements in the entire series if they span a wide range of focal lengths.

And, when putting such products on line, details are often copied from one entry to the next.  I've seen field stop widths copied through an entire line, even though that's impossible.

It's possible to make an element count using a green laser.

But don't be gullible.  A "new" line of eyepieces that comes from a manufacturer that just happens to have the same focal lengths and specs as other brands from the same factory might be different on the outside, but will not be different on the inside.

It's like the APM Ultra Flat Field 10mm, which measured 10.5mm on the test bench.  It comes from KUO and has a 60° field.  There is a 60° 10.5mm in the Premium Flat Field line from the same company with the same element count and overall size.

Is it the same eyepiece?  Yes.  From the manufacturer's standpoint, why reinvent the same eyepiece when you already produce it?

 

[John]

On 31/08/2024 at 14:57, Don Pensack said:

....But don't be gullible.  A "new" line of eyepieces that comes from a manufacturer that just happens to have the same focal lengths and specs as other brands from the same factory might be different on the outside, but will not be different on the inside.

It's like the APM Ultra Flat Field 10mm, which measured 10.5mm on the test bench.  It comes from KUO and has a 60° field.  There is a 60° 10.5mm in the Premium Flat Field line from the same company with the same element count and overall size.

Is it the same eyepiece?  Yes.  From the manufacturer's standpoint, why reinvent the same eyepiece when you already produce it?

 

I'm reminded of the William Optics branded version of the KUO made 100 degree eyepieces - they had it engraved it as being 101 degrees, presumably to get a slight marketing edge over the other brands versions.

A touch of the Spinal Tap amplifiers there I reckon:

"Well it's one louder, isn't it ?" 😁