Louis D

1 hour ago, stormioV said:

I don't think I would get anything out of svbony 8-3 zoom in my SCT.

Probably minimal.  Your f/10 scope at 8mm yields a 0.8mm exit pupil.  I generally prefer to go no lower than 0.75mm.  The Svbony zoom at 5mm would yield 0.5mm which is about my limit for seeing through my eye floaters.  The other problem with your SCT is the very high resultant powers that would require very good seeing conditions (2000/8 = 250x, 2000/5 = 400x).

On 23/05/2023 at 10:33, Artik said:

SKeye uses compass for orientation (and for me was highly innacurate) while AstroHopper relies on gyro - sensors that exists in smart phones for AR/VR and have decent accuracy.

Are you sure about this?  I found this blurb on the SkEye website:

Whenever SkEye is in automatic scrolling mode, SkEye gathers data from two or three sensors in your Android device: the accelerometer, magnetometer and gyroscope (if available).

I've found it accurate enough to put objects within 2 degrees of the optical axis.  It's hard to complain about a free app.

I've taken some images through the KUO 152mm with various filters and compared it against other scopes I own in another thread.  Here are links to the relevant posts:

5 hours ago, Mr Spock said:

How about we do the old fashioned thing and look through stuff instead of getting tied up on technical voodoo 

Sounds like we have a volunteer to take one for the team. 😁

Let us know what you think of them.

1 hour ago, Mark2022 said:

I bought the Altair LER 5mm for the significantly increased eye relief at high power and I also thought this would provide a far brighter image on the camera.

Nope.  Brightness of the projected image is entirely based on the exit pupil of the eyepiece/scope combination.  Any 5mm will yield the same image brightness in the same scope.  The long eye relief will make it easier to match the eyepiece exit pupil to the camera's entry pupil for afocal projection.  I'm not sure it makes any difference for regular eyepiece projection that you're attempting.

Be aware that most eyepieces not specifically designed for eyepiece projection will project a curved focal plane.  You may find it impossible to get the center and edge in focus at the same time on a flat imaging sensor.  This focal plane curvature is not an issue for afocal projection due to the taking lens's depth of focus.

Here's a composite of the KUO 152mm Achromat with no filtering and 8 filter variations to try to both cut violet and sometime red fringing in an effort to increase sharpness and contrast:

The SemiApo is the Baader SemiAPO filter in 2" format.

It's too bad the Hirsch filters are only available used because they had a bunch of unusual colors such as their Light Yellow #12A (Wratten #4) and Light Blue #82B (Light Cyan).

The Green X1 (Wratten #11) and Yellow K2 (Wratten #8) filters are both 48mm Rokunar photographic filters.  Both are still available as new old stock on ebay in 48mm size.

The Cheap Yellow and Green filters came in a set of 6 colors from China for $13.  They tend to cause a bit of light scatter and loss of image fidelity.

The 600nm Shortpass filter (Minus-Red) is an uncut dielectric filter from China.

As in my previous post, the Baader SemiAPO does a very good job at cutting most of the objectionable violet fringing while avoiding adding a harsh yellow cast.

The Hirsch #12A does a good job cutting violet while adding very little yellow cast to the image.

The Yellow K2 is a bit heavy handed.  However, it cuts all but a tiny bit of violet fringing.  I should try pairing it with my 48mm Moon & Sky Glow filter to make a poor man's Baader Contrast Booster and reduce the yellow cast.

The Green X1 is a good compromise to cut both violet and red at a reasonable cost.

The Yellow/Cyan and Yellow/Minus-Red filter combinations do a bit better than the Green X1 by having higher transmission over a broader passband while still cutting almost all violet and red fringing.  However, the components are difficult to find.

I think this eyepiece line aims for high contrast and sharpness on axis with low scatter and stray light, similar to the Vixen HR line.  I'm guessing they accomplish this through use of glass with very little bubbling or surface roughness from polishing.  They probably also have carefully designed light traps to reduce stray light.  If none of this is true, I, too, would wonder what makes them worth the premium price.

As promised, I went out last night and took more comparison images of the moon.  This time, it occurred to me, how close would a 2x Barlowed smaller, but higher quality, scope show relative to the big KUO 152mm Achromat.  I brought out my Astro-Tech 72ED and TS-Optics 90mm FPL-53 Triplet APO for comparison at both native and 2x magnification.  I did the same with the GSO 150mm Newtonian as well.  I skipped Barlowing the KUO 152m Achromat because it did so badly in that mode the night before.

Here is a composited comparison image, this time with labels (ST152 = KUO 152mm Achromat).  Make sure to click it open for a high resolution view.

My impression at the eyepiece was that the 90 APO showed the sharpest, contrastiest views, even when Barlowed.  The 72ED was a bit behind thanks to being an FPL-51 doublet.  The 150 Newt was showing incredible detail, sharpness, and contrast as expected.  However, the APO had more WOW factor due to the high contrast.  All three Barlowed extremely well.

The ST152 was just sad to look through.  The Baader SemiApo filter helped it a bit, but there's just nothing that will make it a compelling bright object scope.  The views were blurred, low contrast, and awash in false color.  I included the "Typical Violet Fringe" image because it best captured how the view looks to the eye at the eyepiece.

I will say that bright star fields looked decent in the ST152 with my 40mm XW despite there being some violet fringing on brighter stars.  I'll have to do a comparison in that mode at some point.  Perhaps it might "shine" for wide field sweeping.

5 hours ago, stormioV said:

That's the reason why I got 3.2mm.  To complete the set.

That's the only one I don't have.  How have you found it to perform under the stars?

My typical go-to A-team favorites would be as follows:

40mm Meade 5000 SWA decloaked

17mm ES-92

12mm ES-92

10mm Delos or 9mm Morpheus (hard to pick between them)

5.2mm Pentax XL

3.5mm Pentax XW

While I really like my 30mm APM UFF, it just doesn't have the wow factor of the SWA for some reason.  Perhaps because it gives up too much (~10mm) in field stop size to the SWA. 🤷‍♂️

3 hours ago, Don Pensack said:

Takahashi identifies those circles as 4 milliradians, which translates to 13.75' in apparent size.

I just google image translated it as 4 microradians (see below), which again would be astonishing if it is 1000x better corrected than an improved Plossl.

Why would they use an Airy disk, which is typically in the 2.5 to 5 milliradians range, for the upper images, and then switch to 4 microradians, 1/1000ths of a typical airy disk, for the lower images?  An apples to oranges comparison is very confusing.

Text:

Center spot diagram comparison
LE12.5

The circle is an Airy disk, 11 wavelengths
from 436mm to 656nm are synthesized,
and the objective is an aplanatic optical system.
(C) TAKAHASHI SEISAKUSHO Ltd.
TPL-12.5 Spot Diagram
Apparent field of view
(half angle)
0°
5.5°
11°
16.5°
22°
A circle is 4 microradians
Afocal calculation of 11 wavelengths
from 436mm to 656nm
(C) TAKAHASHI SEISAKUSHO Ltd.

On 27/07/2023 at 15:20, PeterStudz said:

I think you mean this article…

https://skyandtelescope.org/astronomy-equipment/equipment-diy/dealing-with-dew/

”Then there's the observing umbrella, not a widely known accessory but one that works. A beach umbrella blocks the chill of outer space the same way it blocks the heat of the Sun. It can help shield all your gear and you too from the cosmic deep freeze. On a still night a thermometer under an umbrella can read more than 10° Fahrenheit (6° Celsius) higher than when it is exposed to the open sky.”

I’ve never tried. But in my younger days I’d go wild camping and sometimes use a tarpaulin (open on all sides) in order to keep dew off. 

This article goes on to say the following:

You can take active countermeasures too. A 4- or 7-watt light bulb inserted into a blanketed telescope makes a nice low-power heater. 

Well, the article should probably be updated from its original 2006 published version to specify a 4 W incandescent light bulb because I've got a modern 4 W LED light bulb that is a 40 W incandescent lumen equivalent that emits no infrared radiation, which is I think the form of heating the article desires.  It does emit waste heat from the LED itself, but that is mostly confined to the base and would eventually reradiate as far infrared radiation.  However, an LED light bulb is less efficient at immediately converting electricity purely to heat than an incandescent light bulb because it is optimized to convert electricity into visible light that doesn't warm things very quickly.  I suppose the visible light photons, if contained within a light tight enclosure, would eventually warm whatever they strike in there, so an LED light bulb still might be 100% efficient at converting electricity to heat in the long run.

All the rebrands of the current KUO 4mm UWA should perform similarly.  For example, it's also sold in the US under the Astro-Tech name by CN's sponsor.  Aside from cosmetics, I would think the optics are identical.

I did find this blurb which appears to be a factory-style release statement since Sky Rover is KUO's factory brand:

Compared with the old UWA eyepiece, the new version has mainly made the following improvements:
1. The optical system has been slightly adjusted;
2. The design of metalworking part has been changed. The main body is slender in shape, and the cannula made of stainless steel has better texture.
3. Silicone folding eye cup is adopted, which makes observation more comfortable.

SKY ROVER’s second generation UWA series ultra wide-angle eyepieces, with high-grade optics and impeccable appearance, are products that astronomy enthusiasts are keen on. Its success lies not only in providing an ultra-wide angle view of 82 degrees, but also in its reasonable price. Especially suitable for observing planets and deep space targets, and also suitable for observing ground targets.

So, it's possible the current KUO UWAs are slightly better optically than the original flat top style, assuming the "slightly adjusted optical system" improved rather than degraded the performance.  Notice they didn't explicitly say "slightly improved", so there is wiggle room as to what they did to the optical design.  Perhaps it was slightly adjusted to make it cheaper or easier to produce at the same image quality level.

On 16/07/2023 at 08:30, vlaiv said:

or comparison F/10 4" objective will have size of airy disk at 221.6" or 3.7 arc minutes - about x287 larger circle than presented in the image.

If indeed Tak has managed to reduce the aberration spot size by a factor of 287 over a typical improved Plossl (TV, Clave, Brandon), I will be insanely impressed.

@Marian M Here's some more comparison images from last night using the same setup except with a Parks GS 2x Shorty Barlow, so roughly 144x (achromat) and 120x (Newtonian):

Top Row, Left to Right: GSO 150 f/5 Newtonian unfiltered, KUO 152 Achromat unfiltered, KUO 152 Achromat with Baader Semi-APO filter

Bottom Row, Left to Right: KUO 152 Achromat with Yellow K2 filter (Wratten #8), KUO 152 Achromat with Green X1 (Wratten #11), KUO 152 Achromat with Hirsch #12A Light Yellow (Wratten #4) and Hirsch #82B Light Blue (Light Cyan)

This shows that filtering the unfocused violet and red ends of the visible spectrum can help to sharpen up the achromat's image.  However, I stand by my original assertion that the 150 Newtonian stomps all over the 152 Achromat for image sharpness, contrast, and color fidelity on bright objects.

I'll try and get out tonight to see if I can improve on the achromat's performance any.

On 27/07/2023 at 07:54, Marian M said:

Louis, if I were to give one more chance to the refractor (DSO only), your subjective opinion- which is the aprox magnification where the Newton is becoming crisper than the 152?

Is the 152 yet sharp at 100x? Many thanks again!

Here's a quick comparison I did last night with the KUO 152 achromat (top row images) against the GSO 150 f/5 Newt (bottom row image).  The upper left image is unfiltered while the upper right image is filtered with a Baader Semi-APO filter.  The single Newtonian image is completely unfiltered.  I adjusted the refractor gamma to bring them into alignment exposure-wise with the Newtonian since they were a bit overexposed.  Please disregard the blown out highlights in the upper row as they are simply artifacts of my poor ability to handhold the phone, align it properly, and adjust exposure for afocal projection.

All images were taken with my 12.5mm APM Hi-FW eyepiece using afocal projection with my Galaxy S7 phone's camera.  The upper images work out to 72x while the lower image works out to 60x.  I thought it more important to use the same eyepiece than try to match magnifications.

The violet fringing in the upper left was actually stronger to the eye than what the image shows.  I don't think phone cameras are very sensitive to far violet light.  The Semi-APO image fairly closely resembles reality except for the yellow fringe.  It appeared to be a faint violet fringe to the eye.  I think it's due to the different sensitivities of the eye versus the camera to various wavelengths of light.  The lower left image is accurate except for the brown color cast.  That was due to having issues matching exit and entry pupils handheld.  The absolute lack of color fringing is accurate.

The Newtonian image to the eye was sharp and etched.  The achromat images to the eye were slightly fuzzy edged even filtered.  The violet cast was mostly distracting on high contrast features.  Unfortunately, those are the very things most worth looking at on the moon.  I will say that the Semi-APO filter tamed the extreme violet fringing enough without adding much color cast that I found the image pleasant to view.

I'll try again tonight if I get the chance to see if I can improve on the results.  No guarantees.

22 hours ago, Marian M said:

Also, being so fast (F/4), I presume the second mirror is large. Would that affect the view through a large 2" 40mm eyepiece like Lacerta/ Paragon (secondary being somehow visible?)

I tried out my 40mm Lacerta ED in my 150 f/5 Newt last night on the moon.  While I could detect a slight secondary shadow dimple on the face of the moon, I had to go looking for it.  I wouldn't consider it intrusive at all.

3 hours ago, paulastro said:

I'm still using Adobe Elements 9 for all my image processing, along with an even older steam driven Dell laptop.

Got ya beat.  I still use PSE 2.0 from 2001 for my photo editing.  It came on a CD with a scanner purchase with the activation code printed on the CD sleeve.  I have it installed on multiple machines around the house.  It does what I need and doesn't depend on online activation.  Even after 20+ years, I keep learning new ways use its features.

I do keep an old 2006 XP computer with a PCI to SCSI card for my Minolta slide scanner and a Firewire port for my old MiniDV/HDV cameras.  I've already converted all of my tapes, but my son's girlfriend just came into possession of her childhood tapes, so I'll be converting those for her with that old machine.

Sometimes being a pack-rat pays off.

6 minutes ago, Marian M said:

Happy to discuss the focusers as well here, I am at the beginning of the Newtons curve learning 😄

 

Now, the big question- most of the observations I am using either heavy bino (MB + 2 Morpheus) or large eyepieces (APM XWAs) 

Is this suitable for the above Newton, what about the back focus required for Bino. For all my refractors I did changes that all are accommodating the bino without GPCs, for largest FOV possible. Would that work with the newton? Would be a pity to have a design for large FOV which is destroyed by the GPC

 

Also, being so fast (F/4), I presume the second mirror is large. Would that affect the view through a large 2" 40mm eyepiece like Lacerta/ Paragon (secondary being somehow visible?)

If you tension the cheapened GSO LB focuser enough, it will easily lift heavy loads, just with a bit of stiffness in the action.  I've used it with the GSO CC and a 2 pound eyepiece (40mm Meade 5000 SWA) without issues.

I have the original V1 version of the focuser on my KUO 152 achromat.  It's a beast.  I've not noticed any tendency of it to slip and it is buttery smooth.  It's practically over-engineered.  I have no idea what their current V3 focuser is like, though.  While the V1 focuser has plenty of focuser travel, I'm not sure it would accommodate a BV's needs.

Even on my f/5 GSO Newt, the secondary is fairly large to avoid vignetting because it is intended for imaging.  I've used it with my 40mm SWA mentioned above, and I haven't noticed secondary shadow being an issue.  I can't speak to the f/4, though.  It is one of the reasons I went with the 6" f/5.  I had also read balance is a concern with the 8" f/4 due to difficulty getting the rings and associated dovetail bar in the correct position due to the focuser's location on the stubby tube.

16 minutes ago, Mr Spock said:

It's the same focuser as on my 12" and that works perfectly.

I thought the StellaLyra 12" f/5 Dobsonian comes with the standard GSO 2" Crayford Focuser for Reflectors:

  While the GSO OTA Newts come with a cheapened version of the GSO 2" Linear Bearing Crayford Focuser for Reflectors:

Notice that the pre-tensioning set/grub screws were removed from the GSO LB focuser that is available for purchase separately:

This leads to the problem I mentioned.

Notice that your focuser has at least one pretensioning set/grub screw, so it avoids this issue.

You're right, the standard GSO focuser works fine while the GSO LB packaged with their OTA Newts has the issue I mentioned.

5 minutes ago, Mr Spock said:

I tell you, I'm fancying this setup as a perfect wide field filler for between my 4" Tak and 12" dob. A 8" f4 with coma corrector:
https://www.firstlightoptics.com/stellalyra-telescopes/stellalyra-8-f-4-m-lrn-newtonian-reflector-with-2-focuser.html
https://www.firstlightoptics.com/coma-correctors/stellalyra-2-4-element-photo-visual-coma-corrector-for-newtonian-telescopes.html

I think that would go well on my EQ5 just for wide field visual. It would suit a simple alt-az too.

Swap in the 6" f/5 and it's the same setup I have.  You have to be careful with that dual speed focuser to not reduce tension too far.  If you do, the draw tube drops to the bottom of the focuser.  It's a known issue with it because it has no separate pre-loading tensioner.

I rides fine on my DSV-2B mount while the 152 achro is clearly overloading it.

18 minutes ago, Marian M said:

Louis, if I were to give one more chance to the refractor (DSO only), your subjective opinion- which is the aprox magnification where the Newton is becoming crisper than the 152?

Is the 152 yet sharp at 100x? Many thanks again!

On dim DSOs or bright objects?  I'd say on dim objects, it's fine up to 100x.  For example, I recall the Trapezium looking good at that sort of power.  On bright objects, it needs green filtering to achieve sharpness at any power.  By way of comparison, the 6" f/5 Newt looks good at any power and brightness of object.  If secondary spider diffraction spikes are showing in the Newt, violet and red are showing in the achromat, so there's always a trade off between these two on brighter objects.  However, the Newt is sharp while the achromat is a blurry mess needing green filtration.

5 minutes ago, The60mmKid said:

I hear you! I love refractors, too, but I think that 8"-12" fast reflectors don't receive as much attention as they deserve as relatively portable rich-field telescopes. I can't think of another telescope that would match the bright, wide, pristine views that, say, a 10" f/4 with a coma corrector will provide without being far more expensive and/or heavy. But perhaps others would disagree?

I totally agree.  Even a 6" or 8" f/4 or f/5 Newt with CC yields fantastic wide field views.  You just want to avoid going so large in exit pupil that secondary shadow becomes an issue.  I find my 6" f/5 GSO Newt a joy to use on an alt-az mount.  It's light, holds collimation well, and has sharp, color free images.

3 hours ago, wesdon1 said:

That being said, i still love being outside all night, and I simply watch YouTube vids on my phone sat on my chair next to my rig, drinking hot coffee to keep from freezing to death! LOL. 

Got the image. 😁

1 hour ago, paulastro said:

That's brilliant news, thank you. I thought I might have to buy the cheapest Starsense scope I can find, so that my Starsense future is secured should I happen to live to be 100 years old 😊.

Of course, you bring up the interesting conundrum of corporate support in even 20 years.  Who's to say that Celestron will keep that particular webpage running even that long to kick out your codes to you.  It's also likely the app will no longer work on those future phones due to lack of support, so you'll need to keep your last working phone with Starsense loaded limping along on a long dead dead battery continuously plugged in to a charger.

This isn't that far-fetched.  I'm still using Sky Commander DSCs I bought way back in 1998, 25 years ago.  They're not fancy, but they still work great, and they support realign on object that Starsense does not to refine the alignment.