jetstream

@vlaiv thanks for the explanations, I always like the theory.

I can absolutely see both the Enke minima and Enke gap, back when Saturn was high using my 10" dob (&15"). I cannot see that thin line dividing the gap. My eyes test 20/15 and 20/10 last time checked. I totally agree that there is a difference between resolving and detecting.

@davekelley I do not focus my attention on theory eventhough I enjoy it. What I do when observing is to maximize things in my control ie cooling, collimation and thermals. Once done I then try everything I have on an object-ie magnification etc. Doing this allows you to get to know your own scope and its limits as well as your seeing conditions.

Some objects seem to defy magnification limits ie Saturn and the moon and we can throw Mars in there to.IMHO.

@vlaiv is it possible that resolving stars splits differ from resolving objects such as planets with regard to the MTF for the latter? I find Peachs obervations to be true from my own observing.

from Peach

"Understanding Resolution and Contrast

Two points it is important to understand is the resolution a telescope can provide, and how the contrast of the objects we are imaging affects is related to what can be recorded. Its often seen quoted in the Dawes or Rayleigh criterion for a given aperture. Dawes criterion refers to the separation of double stars of equal brightness in unobstructed apertures. The value can given given by the following simple formula:

115/Aperture (mm.) For example, a 254mm aperture telescope has a dawes limit of 0.45" arc seconds. The dawes limit is really of little use the Planetary observer, as it applies to stellar images. Planetary detail behaves quite differently, and the resolution that can be achieved is directly related to the contrast of the objects we are looking at. A great example that can be used from modern images is Saturn's very fine Encke division in ring A. The narrow gap has an actual width of just 325km - which converts to an apparent angular width at the ring ansae of just 0.05" arc seconds - well below the Dawes criterion of even at 50cm telescope. In `fact, the division can be recorded in a 20cm telescope under excellent seeing, exceeding the Dawes limit by a factor of 11 times!. How is this possible?.

As mentioned above, contrast of the features we are looking at is critical to how fine the detail is that we can record. The Planets are extended objects, and the Dawes or Rayleigh criterion does not apply here as these limits refers to point sources of equal brightness on a black background. In fact it is possible for the limit to be exceeded anywhere up to around ten times on the Moon and Planets depending on the contrast of the detail being observed/imaged."

http://www.damianpeach.com/simulation.htm

I like hyperwides for nebula, starfields and as a finder. For the moon and planets orthos, good zooms and good widefields such as Delos, XW and Delite work well. For galaxies those same widefields and orthos tick the boxes for me.

On 15/12/2019 at 13:17, blinky said:

Nope - Still no better tonight!  After trying again with it on the mount this is the best I got.

 

 

I'm curious- what do you collimate with for your astrophotography work with newts?

19 hours ago, Maniek said:

Hello. 

I have Newton 10 " dobson for several months. Most of the observation także me of the Moon although I like DSO. Let's 70% to 30%.

I would like to build a target set of eyepiece. I look at Televue and after Reading hundreds of posts, comparisions and tests I have chosen this set:

Ethos 13

Ethos 8 

Delos 6

Delos 4,5 

I am asking for grades, opinions and corrections. 

Greetings. 

Should you scratch the 8 Ethos and try an 8 Delos?....

In this range I switch from hyperwides to excellent high transmission widefields, just me.

My 17mm/14mm Nikon HW is very good, possibly a hair better than my 17E. However the design of the eyepiece- a very long bottom extension- makes focusing a challenge and almost eliminates the use of the excellent Paracorr II in my dobs.

The factory eyecup is a joke as are the caps.

The beauty of Televue eyepieces is their performance in fast newts with the Paracorr. A recent conversation with Mr Al Nagler revealed the goal of the Paracorr II and the TV eyepieces-  diffraction limited( at a minimum) across the field of view with very fast newts. Actually, after this conversation I have a new respect for Televue and Mr Nagler.

@John the Docter is a unique eyepiece and a very good one. Eyeplacement can give some fits but it might work with Paracorr, we'll see. Televue has a whole line up of Ethos, Docter or I guess Noblex now, has all their eggs in one basket so to speak.

@Louis D the Nikon 14mm HW EIC is not as sharp as the Docter 12.5mm UWA as tested in my TSA 120, to my eyes.  It is very hard to "out sharp" the sharp Docter. But as I say this is a one of a kind eyepiece. It also does not have as high a DSO transmission ( galaxies) as the Doc IMHO. The Delos on the other hand does.

Fun stuff trying out eyepieces lol!

4 hours ago, Piero said:

In order to tackle the remaining astigmatism, on Gerry's suggestion

You mirror cell is looking more and more like my Astrosystems

I only related to Piero what I knew worked and why- the Astrosystems cell has many nuances that can be overlooked but careful examination reveals a well thought out cell that works in the real world.

Piero, Kudos to you for figuring out the mirror sag!

1 hour ago, Alan White said:

Eye placement and comfort, just didn't work for me.
Kidney bean hell, but wow what clarity.

The DeLites are more comfortable for me, don't kidney bean with me and deliver great clarity too.
As I said, we are all different and what suits one, does not suit another.
 

Thanks Alan, I value honest opinions and related experience. We all have likes and dislikes when it comes to equipment and for me scatter control is on the top of my list.  Congrats for owning the DeLites, a very nice choice.

8 minutes ago, Alan White said:

I have had a Pentax XW 10mm, very nice indeed, but it and I did not gel.

As an interested, potential XW customer can I ask why?

On 09/12/2019 at 15:31, Andrew Singleton said:

I was kindoff hoping someone would look at my pic and tell me whats wrong but i guess its not that easy! 

Does your secondary look round when looking through the bare focuser? Just curious.

Would a 10mm Pentax XW or 10mm Delos fit the bill?

I like sharp and contrasty and with little scatter. The 10mm BCO is a very good low cost option that can match most any eyepiece assuming you get a "good" one. I havn't heard of many mediocre ones just a couple.

My 10mm Delos is excellent and will get the 7mm and 5mm XW's to fill the slots someday. The Delos series is rumored to be the "deepest" widefield out there.

Televue has a nice discount going on...

48 minutes ago, markse68 said:

There seems to be a thin silvery laminate embedded in the inner felt boot- no separate insole

I put silver insoles in my light boots and it made a big difference, slowing heat loss through the bottom of the boots. I wore them all day here with no cold feet as I was moving around putting up my lighted Christmas snowmen.

13 hours ago, markse68 said:

On the look out for some thin cork/aluminium thermal insoles too- decathlon didn’t have any

Did these Sorels have the silver insoles in them in addition to the felt? Those silver insoles really do work. My Baffins liners are reflective covered thinsulate or something like that.

On 09/12/2019 at 20:56, Stu said:

I picked my Muck boots up from the children today.

These are excellent boots Stu, many here are going over to them as they seem tougher in the construction role. I might pick up a set myself. My Baffins are massive...

On 09/12/2019 at 18:12, Littleguy80 said:

The Sorels arrived today.

Right now its -37c here tonight with the wind. With your new boots you could stand and observe for many hours in this with no ill effects.

I wonder if anyone can tell me how the 30mm XW compares to others, say an ES 82 30mm in the scatter department? I would love a truly low scatter, low power widefield eyepiece.

I was wondering if anyone has tried using a USB microscope held up to a telescope eyepiece? Would it work on DSO? Still thinking of the Celestron.

@Alien 13 and @johninderby maybe you guys have some insight into this? I'm still pondering the gift for the 10 yr old grand daughter and thought it might be awesome if one of these devices could "image" real time, even if not perfect.

Any and all advice welcome, thanks, Gerry

2 minutes ago, Ships and Stars said:

Just getting time to view is my main problem

Yes, time can be an issue, here its the year of clouds/snow and rain. I was 90 miles north yesterday, clear as a bell into evening and drove into a wall of cloud not too far from this place. I guess thats why they call it Rainy Lake lol!

3 hours ago, Ships and Stars said:

I am now looking at a low profile Crayford focuser

I would hold off... everything is working well for you, I would just stick some 30-32mm eyepieces in the binoviewers and observe.  So far I havn't got things to work well with filters in this type of set up.

Big controversy with bino prism clear apertures including mine... mine are 27mm clear at the "zero" 2.3x but the reducer or whatever is in there reduces it a bit.

My humble advice? don't worry about clear aperture. "run whatcha brung"!

btw 25mm plossls work well too.

31 minutes ago, Ships and Stars said:

Good point Gerry on the exit pupil through binoviewers - I didn't realise that about splitting the exit pupil, but it makes perfect sense.

At f4.8 the I wanted to go lower mag than the 32mm's give. At f4.1- not tried yet- I think the 32mm range will be VG. As we know we have to deal with secondary shadow on brighter objects if the mag gets down there.

You might want to consider this for your upcoming purchase....

No need for fancy, expensive eyepieces with the binoviewer IMHO, GSO plossls are VG for example. I like plossls vs orthos for this application because the plossls eye relief is tighter and not as prone to float, eventhough the 32mm TV's do float without the eyguard extender.

One on my very best views of the Needle galaxy,NGC4565 was with the15", Binotron 27's/32mm TV plossls/powerswitch at 1.3x. Another stunning view is the Leo Triplet, along with M42, M57 etc...

A 20" fast f4 scope should be super on these objects with the right eyepieces.

@Ships and Stars

From CN former mod EdZ, an important read

" Exit Pupil
A telescope with binoviewer produces what I would call a false exit pupil. The exit pupil is always larger than the amount of light that it delivers (as compared to exit pupil from scope without binoviewer). That is due to the fact the beam splitter delivers half the light to each exit pupil. This mathematics is all discussed above.

Think about it. A 6" scope with binoviewer at 30x has a 5mm exit pupil. But the light delivered to that exit pupil in each side of the binoviewer is (150x150)/2 = 11250, then sqrt11250 = 106mm. The true exit pupil would be 106/30 = 3.5mm, or an exit pupil with one half the area of the false exit pupil.

The light delivered to the exit pupil in a binoviewer is not as bright as the light in an equal sized exit pupil from either a scope or binocular. Hence, it can be described as a false exit pupil."

https://www.cloudynights.com/topic/61467-binocular-vision-summation/
 

6 hours ago, AstroNinja said:

I am on my second pair of North Face Chillkats and I have a pair of the Baffin Impact boots. Both very good

Jon

My wife uses Baffin Impacts and as you say are excellent.

21 minutes ago, Ships and Stars said:

put the now infamous single use plastic bags on your feet

When I was young, we all did this lol! All the little kids back then walking to school in -30+c. Now they shut the schools down and most all kids catch the bus.

2 hours ago, Alan White said:

I tried other 32mm Plossl but then came back to the TeleVue 32mm.
Used either without extender and with or without glasses, 
but also have the DiopTrx for my astigmatism.

 

You should see the moon, along the terminator with the 15"/Binotron 27's/32mm TV plossls..... powerswitch at 2.3x

The view never ceases to stop me in my tracks.