The Peashooter and the Light Thimble

[Stu]

Seeing the beautiful crescent Moon this evening prompted me to put the Telementor out for a quick look this evening, which turned into a longer look! This scope is so quick and easy to setup that it has become a regular favourite. I’ve just added a simple helical focuser and that really does help nail the focus.

The views with the 24mm Panoptic at x35 were beautiful, and after a while the earthshine started to show as it got dark enough; stunning!

Refering to my Moon Maps app (credits/copyright info shown, I thoroughly recommend the app), I located every crater and feature shown, with the exception of a rille in a Cleomedes, but to be fair the crater floor was still in darkness so I couldn’t try for it. I popped the Nag Zoom in giving x140 which was great for some of the finer features and detail around Mare Crisium, but I preferred the Leica Zoom at around x60 I guess (a bit above lowest power), just enough mag, earthshine showing beautifully and framed comfortably. Really nice.
 

Checking the forum whilst warming up for a while, I saw @robhatherton’s post about Izar, so decided on a little challenge with the Peashooter 63mm Telementor vs it’s reflector buddy the 65mm Light Thimble TAL Alkor!

I put the TAL out on my Ercole Mount which handles it with ease, and had a crack at Izar. The focuser on the TAL is just a little too free running for my liking but is tricky to tension up, so finding focus is a slightly delicate process. This scope comes with an eyepiece, Barlow and spacer which give the following. Eyepiece alone, x33. Eyepiece and Barlow, x88. Eyepiece, spacer and Barlow, x133. I have also found that you can pull the eyepiece and spacer out from their seating to extend the space between the Barlow and the eyepiece to increase the mag further, I’m guessing to x150 or perhaps a little more. Using x133, when the seeing settled, the secondary was clearly split, showing a greyish colour contrasting with the primary and sitting plum on the first diffraction ring. The collimation on this scope is pretty much bang on after I tweaked it on first receiving the scope, and when the seeing is good, the star images are beautiful, with a textbook diffraction ring.

Going to max power plus did increase the separation and led to an even clearer split. Really nice. Whilst at it, I had a look at Castor and Algieba, both beautiful white pairs of unequal bullet holes on black.

Moving to the Telementor, it was a similar experience really, even better perhaps. At max zoom with the Leica, giving x94, it was a clear split again, showing that it was a little easier in this scope not unexpectedly given the clear aperture. Dropping to x88 on the TAL didn’t allow a split, nor did increasing this a bit by extending the distance between the Barlow and eyepiece giving x100 ish I guess.

Castor and Algieba were pretty similar in both scopes, both very easy.

Finally, I spotted Vega above the hedge with the promise of the Double Double to complete the challenge. The Telementor managed it clearly at x94, and it was still possible with reduced mag down to say x80 ish. Moving to the TAL, it was clear at x133, and still possible at x88 although getting tough, particularly the more unequal of the two pairs. I even managed to spot M57 dimly in the TAL, not bad for a 65mm scope under light polluted skies.
 

I do keep my interest fresh by trying to get the most out of these smaller scopes and seeing just what they are capable of; which is actually quite a lot! I think that smaller refractors often have an easier time of it vs larger newts when splitting some of these doubles, the stars are so clean and tight it really helps with the split. The little Newt does an amazing job too, and is pretty close to the Telementor in terms of image. It must have the tiniest secondary there is!

A fun little evening I must say.

[Littleguy80]

Ace report, Stu. It’s like aperture fever works in reverse for you 😂 Very much goes to show that a lot can be achieved with good optics and a skilled observer. 

[chiltonstar]

Small scopes can give a lot of pleasure, particularly on bright easy targets like Izar.

This is a simulation of how Izar appears with aperture (refractor) using Aberrator:-

Chris

 

[Stu]

48 minutes ago, Littleguy80 said:

It’s like aperture fever works in reverse for you

Yes! Very true Neil. The challenge gets bigger the smaller the scope!

[John]

Great report Stu !

I have a rather old copy of the Broadhurst Clarkson and Fuller catalogue (bookalogue as they called it) which dates to around the time that the little Tal 65 became available over there. Dudley Fuller says in there that he rarely recommends scopes of less than 3 inches aperture but he was delighted to make an exception for the Tal Alkor becuse it has exquisite optical quality, excellent design and is over-engineered in a way that you just don't find in the average scope of this aperture.

Your experiences confirm Dudley's views I think

[Stu]

21 minutes ago, chiltonstar said:

Small scopes can give a lot of pleasure, particularly on bright easy targets like Izar.

This is a simulation of how Izar appears with aperture (refractor) using Aberrator:-

Chris

 

That’s interesting Chris. I must say the view was more like the 80mm simulation, well defined single diffraction ring and clear separation between primary and secondary, they were much tighter stars than shown in the 60mm example.

It is interesting that many still struggle to split it in larger reflectors, I assume that is related to seeing conditions affecting these more, and the less compact star shapes despite the increased resolution?

[chiltonstar]

3 minutes ago, Stu said:

That’s interesting Chris. I must say the view was more like the 80mm simulation, well defined single diffraction ring and clear separation between primary and secondary, they were much tighter stars than shown in the 60mm example.

It is interesting that many still struggle to split it in larger reflectors, I assume that is related to seeing conditions affecting these more, and the less compact star shapes despite the increased resolution?

I suspect that, with small apertures the separation often looks better than it really is because the pair of stars are much dimmer, whereas larger apertures sometimes appear to "fill the space" between a pair of stars with light. I've certainly found that a pair appears to be visually better separated with my 180 Mak if I use a ND filter.

As you say, it is all seeing dependent! 

Chris

[Littleguy80]

28 minutes ago, Stu said:

That’s interesting Chris. I must say the view was more like the 80mm simulation, well defined single diffraction ring and clear separation between primary and secondary, they were much tighter stars than shown in the 60mm example.

It is interesting that many still struggle to split it in larger reflectors, I assume that is related to seeing conditions affecting these more, and the less compact star shapes despite the increased resolution?

This has been quite noticeable to me since I’ve had the 80mm refractor. The splits are often cleaner than the 10” dob, needing less magnification. If seeing is good then the dob does a great job. I had a really nice view of Tegimine with it recently, splitting down to three component stars. I’ve also had times where I thought something was wrong with the dob because I couldn’t get a decent view of Izar. The frac seems to be a bit more consistent. 

[Stu]

15 minutes ago, Littleguy80 said:

This has been quite noticeable to me since I’ve had the 80mm refractor. The splits are often cleaner than the 10” dob, needing less magnification. If seeing is good then the dob does a great job. I had a really nice view of Tegimine with it recently, splitting down to three component stars. I’ve also had times where I thought something was wrong with the dob because I couldn’t get a decent view of Izar. The frac seems to be a bit more consistent. 

Yes, that’s certainly my experience Neil. Dobs need good seeing to perform well on doubles but the fracs (and tiny newt!) deal with variable seeing much better. Although a larger newt may be capable of splitting tighter doubles under the right conditions,  I just enjoy views that much more in a frac! 

[Stu]

28 minutes ago, chiltonstar said:

I suspect that, with small apertures the separation often looks better than it really is because the pair of stars are much dimmer, whereas larger apertures sometimes appear to "fill the space" between a pair of stars with light. I've certainly found that a pair appears to be visually better separated with my 180 Mak if I use a ND filter.

As you say, it is all seeing dependent! 

Chris

Thanks Chris, that makes a lot of sense.

[Stu]

I’ve just noticed the rusty Munsen rings on the TAL! Might have to get some black paint on those!

[Littleguy80]

10 minutes ago, Stu said:

Yes, that’s certainly my experience Neil. Dobs need good seeing to perform well on doubles but the fracs (and tiny newt!) deal with variable seeing much better. Although a larger newt may be capable of splitting tighter doubles under the right conditions,  I just enjoy views that much more in a frac! 

The other thing that I’ve noticed is that the colours seem more vibrant in the frac. Definitely adds to the appeal of using the smaller scope for that type of observing. 

[John]

The view of Izar the other night with my Tak FC-100DL at 281x was very like the 200mm Aberrator image. Really tight stars and a big gap.

 

[Stu]

On 26/04/2020 at 09:50, John said:

Great report Stu !

I have a rather old copy of the Broadhurst Clarkson and Fuller catalogue (bookalogue as they called it) which dates to around the time that the little Tal 65 became available over there. Dudley Fuller says in there that he rarely recommends scopes of less than 3 inches aperture but he was delighted to make an exception for the Tal Alkor becuse it has exquisite optical quality, excellent design and is over-engineered in a way that you just don't find in the average scope of this aperture.

Your experiences confirm Dudley's views I think

They really are amazingly capable little scopes John, and the eyepiece/Barlow system is simple and easy to use. I much prefer it on a regular mount although I do have the original.

[chiltonstar]

9 hours ago, Stu said:

They really are amazingly capable little scopes John, and the eyepiece/Barlow system is simple and easy to use. I much prefer it on a regular mount although I do have the original.

 

[chiltonstar]

On 26/04/2020 at 09:50, John said:

Great report Stu !

I have a rather old copy of the Broadhurst Clarkson and Fuller catalogue (bookalogue as they called it) which dates to around the time that the little Tal 65 became available over there. Dudley Fuller says in there that he rarely recommends scopes of less than 3 inches aperture but he was delighted to make an exception for the Tal Alkor becuse it has exquisite optical quality, excellent design and is over-engineered in a way that you just don't find in the average scope of this aperture.

Your experiences confirm Dudley's views I think

But presumably, despite the excellent optical quality, they are not able to beat the laws of diffraction though? 65mm is 65mm........

Chris

[John]

26 minutes ago, chiltonstar said:

But presumably, despite the excellent optical quality, they are not able to beat the laws of diffraction though? 65mm is 65mm........

Chris

I'm sure that is true.

 

[Stu]

21 hours ago, chiltonstar said:

But presumably, despite the excellent optical quality, they are not able to beat the laws of diffraction though? 65mm is 65mm........

Chris

Of course you are right Chris, but it is curious when such a tiny scope can appear to outperform larger ones when trying to split some of these double stars. I understand that resolution has a big impact, but have always found that larger scopes have not necessarily performed as well as they theoretically should on these targets. Looking back at your Aberrator image, I actually think the view in the 65mm was a combination of the 60mm and 100mm. The secondary star was positioned on the 1st diffraction ring as in the 60mm example, however the star tightness was much more like the 100mm, with clear separation between the two stars.

I guess I just enjoy viewing these doubles more through smaller scopes than larger ones; I enjoy the Double Double way more in my Tak than in any larger aperture compound or reflecting scope. Just personal preference I guess?

[chiltonstar]

1 hour ago, Stu said:

Of course you are right Chris, but it is curious when such a tiny scope can appear to outperform larger ones when trying to split some of these double stars. I understand that resolution has a big impact, but have always found that larger scopes have not necessarily performed as well as they theoretically should on these targets. Looking back at your Aberrator image, I actually think the view in the 65mm was a combination of the 60mm and 100mm. The secondary star was positioned on the 1st diffraction ring as in the 60mm example, however the star tightness was much more like the 100mm, with clear separation between the two stars.

I guess I just enjoy viewing these doubles more through smaller scopes than larger ones; I enjoy the Double Double way more in my Tak than in any larger aperture compound or reflecting scope. Just personal preference I guess?

Whatever turns you on, as they say! The Aberrator images vary of course according to brightness (and mag), turn up the intensity and you appear to expand the stars somewhat - I think this is roughly what happens sometimes when you use a larger scope. However, I don't think you can beat the Dawes limit with a smaller scope!?

Chris

[Stu]

36 minutes ago, chiltonstar said:

However, I don't think you can beat the Dawes limit with a smaller scope!?

Chris

No, I’m not suggesting you can Chris. Will have to give Pi Aquilae a go just to prove you correct!!