Louis D

Mine is mounted on the back on the finder shoe via a three way extender and a finder shoe to QuikFinder adapter.  That way, I can still mount a RACI there as well as a laser sight via this adapter.

@Don PensackIs this what the image erecting Barlow you remember looked like?

4 hours ago, Don Pensack said:

An erect image can be done with lenses only.  When I was young you could buy what looked like a Barlow lens that would correct the image if inserted before the eyepiece.

At least one company has created an eyepiece incorporating this:

https://khanscope.com/products/image-erecting-eyepiece-1-25-sm-1-25ie

There are a ton of these on eBay.

Note: I suggest dealing with the upside down image.  These are horrible optically.

Are you sure these aren't using a roof-like prism assembly like the erecting eyepiece in this CN teardown?

Compare images of the two eyepieces:

Sky Mentor from Khan Scope:

Celestron 20mm Erecting:

It's not definitive, but I suspect they're similar in design.  If so, here's the internal prisms:

3 hours ago, John said:

I found that the 4mm Radian showed a sort of halo of light when observing the moon's terminator that extended on the opposite side of the field of view to the illuminated portion of the lunar surface. The 3mm Radian did not seem to show this. Was this SAEP ?

That just sounds like poor stray light control.  Not awful, just not optimal.

SAEP manifests itself as full blown blackouts midway across the field from center to edge in the worst cases or simply as fleeting shadows that cause consternation because you can't get comfortable viewing the image.  In both cases, slight head or eye movements in any direction (left, right, up, down, in, out) cause the shadows to dance around giving a nervous or jittery aspect to the image.  Never does it manifest itself as a halo of light.  It's always a lack of light.

35 minutes ago, Don Pensack said:

Could be a matter of focal lengths used.  In general, SAEP is less of an issue with small exit pupils.

It also depends on usage.  If you do a bunch of lunar, solar, or spotting scope usage, or observe under severely light polluted skies, your pupils will be constricted, making SAEP more obvious.  Fully dark adapted viewing minimizes SAEP annoyances.

I was able to see Jupiter's moons with both a Nat Geo 40mm refractor and a Celestron FirstScope 76 at a star party after getting them properly focused and on target for the owners who had brought them to get assistance.  It's definitely possible to do basic astronomy with really poor, big box store telescopes.  It just takes experience and knowledge to work out the issues.  That, and tempered expectations of the views.

I will say that the Nat Geo cheap photo tripod-type mount is the absolute worst.  It's so herky-jerky and wobbly that you have to loosen up everything and keep a steady fist around the mount axes to use it successfully.

I never could get on with the Radians since they were released in 1998.  They just had too much SAEP for me.  I ended up getting Pentax XLs instead and continue to use them to this day.  Many folks report not being bothered by the SAEP, though.

17 hours ago, mrsbuzzy said:

I had settled on the Skywatcher 200p, however, I can't get it until sometime after New Years. So, I have some decisions to make.  Thank you everyone.

Make it a Valentine's Day gift.  He'll love it. 😉

7 hours ago, Stu1smartcookie said:

lol if they were then whoever owns them have two less satellites as they burnt up

  

Were you watching them "burn up" through the eyepiece or naked eye?  I took you to mean through the eyepiece, which would be impossible to do.  I've never seen a slow moving meteor naked eye.  Perhaps y'all have different meteor showers there than here in Texas.  The only thing equivalent to a meteor I've seen that was slow moving was the Space Shuttle returning from orbit over Texas.  It took several minutes to cross the sky.

On 13/12/2020 at 02:46, Stu1smartcookie said:

I even got to see a few meteors which were pleasingly slow moving. 

More than likely they were satellites.

A 2" diagonal forces you to move the primary mirror forward to account for the extra optical path length of the 2" vs 1.25" diagonal.  This increases your working focal length and contributes a bit of spherical aberration to the image because you are no longer at the optimal, design focal length.  Both effects are minor for most folks visually.  There are quality 1.25" diagonals from GSO and others out there.  You're never going to get truly wide fields from a C9.25 anyway.

That's like asking a parent to choose a favorite child. 😲

How about we try to debug what is going on with your current scope?  I've gotten decent images even from "crap" scopes at low powers and on axis (in the center).  It's usually the mounts they come with that are abhorrent.

What is it?  Can you post some images of it on here?  Can you describe the views through it during the daytime at distant targets?

Can you loosen all of the secondary mirror's screws, and then see if it tips enough to point straight at the primary mirror?  You also need to ensure it is rotated such that it looks like a circle in the sight tube.  That part is fairly straight forward.

Once you have the secondary square on with the focuser (round circle) and tipped properly, tighten up all the screws little bit by little bit, readjusting at each step as needed.  Once that is done, you shouldn't need to touch your secondary again.  They generally don't shift between uses.

I just discovered that Ernest in Russia tested this eyepiece back in late September.  My report was even mentioned up above.  Ernest panned my report as being methodically flawed, though he didn't expound on this point very much other than mention unknown distances from ruler to exit pupil.  The distance from ruler to focal plane is fixed, though, as the tripod and ruler never moved.  Regardless, my numbers for the field stop, apparent field of view, effective field of view, and eye relief if you use my value to see the field stop are all pretty close to his.  He didn't even bother trying to quantify as I did the usable field that is mostly SAEP free.

I do disagree with his assessment that SAEP is not an issue at night.  Under my light polluted skies, my pupils will not dilate far enough to cope with the extreme SAEP (largest he has ever measured!).  Maybe at a dark sky site, but not in my backyard.

He also fails to mention that the 25mm ES-100 has a 94 degree eAFOV as well due to rectilinear distortion, so neither is a "true" 100 degree eyepiece.  Each eyepiece comes at the same eAFOV from two different directions distortion wise (angular vs rectilinear).  He also arrives at the 90 degree eAFOV value by plugging the claimed 26mm FL rather than the measured 25mm FL.  Since both are the same for FL and field stop diameter, they have the same eAFOV.

I was surprised that he measured the MWA to have a 25mm focal length instead of 26mm.  I did a pixel count of the center section where distortion is lowest and did a comparative analysis against known good eyepieces to arrive at a measured FL value of 25mm as well.  I don't know how Ernest measures it, but I'm glad he does because I don't normally check this.  I'll have to amend my value for eAFOV as a result to 94 degrees now.

I've used a black nickel plated ball bearing at one end my darkened house lit by a tactical LED flashlight (torch) next to the scope at the other of the house.  That produced a very fine specular highlight.  The black nickel plating reduced other reflections a bit by being darker than chrome plating, but has little effect on direct, specular reflections.  It makes it easier to see the shape of the reflection when analyzing aberrations or collimation.

3 hours ago, Voyager 3 said:

I think I'm going to reign supreme here 😁 ... 41°C in mid may is common here at my location . I donk what's there but 38°-39° , mmm not much of a difference but 39°-40° is mind boggling 😂.

110F=43C, which we hit many summers here in Texas, and 118F=48C, which is fairly common in Phoenix.  Imagine spending 90 days at or above 38C with high humidity.  Basically, mid-June through mid-September is spent entirely indoors in the A/C here.  Phoenix spent 144 days above 100F=43C this past summer, which was a new record for them.  Of course, it's a dry heat there. 😉

5 minutes ago, Tiny Clanger said:

I have friends who moved to the USA years ago , and I visited them when they lived in Scottsdale Az . I recall  seeing a t-shirt which pictured two vultures perched on a longhorn cow skull : one vulture was saying to the  other :

"Yeah, but it's a dry heat ..." 😀

I've been in 110F humid heat in St. Louis and 118F dry heat in Phoenix.  I'll take the dry heat any day.  If you drink lots of water, the dry heat is tolerable.  There's just no way to stay cool in humid heat that high.  I was starting to suffer heat exhaustion until I retreated to air conditioning that day.  That despite drinking 1.5 liters of water in 2 hours.

My favorite vulture cartoon is the following Far Side:

13 hours ago, Tonny said:

For now I decided that I can extend the budget a little bit in order to buy this: https://www.firstlightoptics.com/reflectors/skywatcher-explorer-200pds-heq5-pro.html
This one looks like good for observations and also not bad for AP. Is it good enough or still two scopes is better, considering that I am aware I cant achieve perfect quality photos with one universal type of telescope?

You do realize that setup weighs about 36kg or 79 pounds when all set up?  It has to be assembled in parts and can't be easily moved around once assembled.  This can be an issue if you have trees or buildings to dodge to see certain areas of the sky.

11 hours ago, LukeSkywatcher said:

80F=26C. Damn that's crazy for Feb. Here in the UK and Ireland, that's a heatwave during Summer.

We hit 91F on February 15, 2019.  That's 33C I guess.  Of course, it's a dry heat that time of the year.

It's nice having mostly warm winters, though, to make up for our excessively hot summers.  For instance, we had 90 days above 100F (38C) in 2011.  It was pretty miserable that year.  Y'all would probably melt if that happened in Ireland.

The RDF base may need shimming to get it better aligned with the main optical tube so the adjustment screws can do their job.

On 03/12/2020 at 20:56, johninderby said:

If only a real enthusiast could buy Meade and turn it back into something like it used to be. Not holding my breath. 🙁

https://www.bkalerts.com/recent-bankruptcy-cases/california-central-bankruptcy-court/8:19-bk-14714/bankruptcy-case-meade-instruments-corp

Orion did try to purchase Meade, but as this media quote below says, they were outbid by two Chinese companies.  I think Meade would have been better off under Orion ownership.

Orion had tried to acquire the then financially ailing Meade but was outbid first by another Asian manufacturer and finally by Ningbo Sunny. Orion alleges that after the Meade merger with its Chinese buyer, Orion’s ability to buy products from the combined entities ended.

4 hours ago, Ships and Stars said:

The sun won't directly shine on our house again until late January I think, and even then, it will only be for a few minutes.

Viganella, Italy and Rjukan, Norway both use mirrors on nearby ridges to reflect light into their town squares during the winter since they're also in perpetual shade at that time.  I wonder if you could work up a similar solution. 😉

46 minutes ago, Stu said:

That’s why it is so much easier to get sunburned in summer with the sun high in the sky and with much less atmosphere to travel through.

We learned the hard way that it is still easy to get sunburned in Texas in the winter.  My niece was visiting in early February one year.  We went for a hike in a state park in an area with little tree cover.  Because it was in the 80s, she just wore a sleeveless top to stay cool.  She got the worst sunburn on the tops of her exposed shoulders.  Lesson learned, we're pretty far south, so even in winter, the sun can still be intense.

1 hour ago, Grumpy Martian said:

It is deceptively darker than the mid day Sun at the height of Summer.

I guess you've rarely trekked across a snow covered field in winter under a noon sun.  It is still blinding bright.  I had wear reflective sunglasses back in the 80s to make it bearable to walk between classes during my college days in the upper Midwest.