Maximum Magnification

[wookie1965]

Can anyone help I have heard that the Tal can take a lot of magnification especially on the Moon and Planets, I have a 5mm BST Starguider and I have no inward travel to focus it just about gets it. I have tried a 2x Barlow with my 8mm but that would not even focus. A very good friend was going to give me a TMB 4.5mm but I had to say I would not be able to focus with it. Will the Tal take more magnification and if so could there be something wrong with the focuser. Thank you all.

[John]

The TAL 100 should handle 200x magnification if the conditions are good and the target benefits from it. On close double stars you might even find that 225x or even 250x works.

Short focal length eyepieces needed to get these magnifications should focus at the same point as longer focal length eyepieces from the same range but using a barlow lens does change the focus point and if your focuser has a limited range of travel (which some of the early TAL 100's did) you may well have problems getting the eyepiece to focus. This is nothing to do with the amount of magnification being used though, just a mechanical issue in terms of a shortage of inwards focuser travel. You might find that another brand of 5mm eyepiece (without a barlow) will reach focus fine.

Tele Vue eyepieces seem to reach focus around 8mm futher out (so they need less inward focuser travel) than many other brands but there are probably others as well.

 

 

 

 

[wookie1965]

Thanks John, 

                     I knew that it would take more mag thought I had read that it would and now you have confirmed it. I have a Meade 4000 6.4mm and that only just reaches focus. Hopefully we get clear skies at the meet in November I can get Nick have a look through it and I`m sure he will have a couple of different eyepieces I can try. I may have to save up and get a Televue, do they do a 4.5mm that will be x222 probably maximum mag I can go for.

[Doc]

I have a Tal100r as well, it's one of the original ones with the purple lens and I often use 4mm on the moon so that's x250. It handles it pretty well if the seeing is good.

[wookie1965]

I`m not sure what it is now then like John has said could be the eyepiece dont think it will be the diagonal I have one of these in it.

[John]

The 2" diagonal does use up more focuser travel than a 1.25" does so that might be why you are struggling to get some eyepieces to reach focus with the TAL 100 ?

I've never used a Tall 100 with a 2" diagonal - just the stock TAL 1.25" units.

 

[Ricochet]

For the second time in a single thread John posts what I was going to say before I can finish typing. 

[wookie1965]

Don`t say that I did get the Diagonal second hand cheap but I sold my Tal diagonal to re coop some money. I wonder if I could swap mine for a 1.25 with someone. I will ask Nick has he got a Diagonal to try in case it is that. Thanks a lot John much appreciated.

[wookie1965]

24 minutes ago, John said:

The 2" diagonal does use up more focuser travel than a 1.25" does so that might be why you are struggling to get some eyepieces to reach focus with the TAL 100 ?

I've never used a Tall 100 with a 2" diagonal - just the stock TAL 1.25" units.

 

John I have a 2" to 1.25" which measures 4 cm and a 2" to 1.25" self centering adaptor measuring 3.1 cm would that give me more inward travel do you think. 

[Stu]

16 minutes ago, wookie1965 said:

John I have a 2" to 1.25" which measures 4 cm and a 2" to 1.25" self centering adaptor measuring 3.1 cm would that give me more inward travel do you think. 

It's the distance from the shoulder to the top which makes the difference Paul. You can get very low profile adaptors which may help, like this:

https://www.teleskop-express.de/shop/product_info.php/info/p767_Baader-Reducer-2----1-25---15A-with-only-1mm-optical-length.html

[wookie1965]

Cheer`s Stu just been looking for something that will be great just have save a bit now get one.

[wookie1965]

13 minutes ago, Stu said:

It's the distance from the shoulder to the top which makes the difference Paul. You can get very low profile adaptors which may help, like this:

https://www.teleskop-express.de/shop/product_info.php/info/p767_Baader-Reducer-2----1-25---15A-with-only-1mm-optical-length.html

Is this the same Stu https://www.firstlightoptics.com/adapters/baader-low-profile-eyepiece-adapter-for-steeltrack.html

[Stu]

8 minutes ago, wookie1965 said:

Is this the same Stu https://www.firstlightoptics.com/adapters/baader-low-profile-eyepiece-adapter-for-steeltrack.html

Yep, that's the same one, so I don't think you can get any shorter than that.

[wookie1965]

14 minutes ago, Stu said:

Yep, that's the same one, so I don't think you can get any shorter than that.

Thank you very much should give me a few more millimetres inward travel may even be able to use  a 4mm. Appreciate you taking the time and everyone else.

[Stu]

26 minutes ago, wookie1965 said:

Thank you very much should give me a few more millimetres inward travel may even be able to use  a 4mm. Appreciate you taking the time and everyone else.

If you are going to buy one, it may be worth just holding the eyepiece in a similar position to see whether it gives you enough extra. Otherwise could be a waste.

[wookie1965]

I've emailed FLO and asked them they should know don't think they would sell it to me if it would not work. 

[John]

Those low profile adapters are very good but, ideally, you need to have a recess in the top of your diagonal 2" inch eyepiece tube to accomodate the set screw of the adapter to allow it to fully insert and get the maximum benefit from them I think. FLO will advise I'm sure but they will need to know the make and model of your diagonal. The Telescope Services site advises you that there are other ways to use the adapter if you don't have this recess but you need to consider if they will suit your needs.

 

 

[Stu]

16 minutes ago, John said:

Those low profile adapters are very good but, ideally, you need to have a recess in the top of your diagonal 2" inch eyepiece tube to accomodate the set screw of the adapter to allow it to fully insert and get the maximum benefit from them I think. FLO will advise I'm sure but they will need to know the make and model of your diagonal. The Telescope Services site advises you that there are other ways to use the adapter if you don't have this recess but you need to consider if they will suit your needs.

 

 

When I've used one in the past John, you can remove the set screw and then adjust the grub screws (which are plastic) so they are a tight push fit. Then you clamp it in the 2" diagonal and can easily change eyepieces without needing to use the set screw.

[John]

20 hours ago, Stu said:

When I've used one in the past John, you can remove the set screw and then adjust the grub screws (which are plastic) so they are a tight push fit. Then you clamp it in the 2" diagonal and can easily change eyepieces without needing to use the set screw.

Yes - thats what the TS site advises

I just wondered, if the scope is on an EQ mount, whether the eyepiece would be held securely enough at some of the angles that the diagonal might find itself at

But as long as the way this works is known about, the choice is an informed one

[Stu]

59 minutes ago, John said:

Yes - thats what the TS site advises

I just wondered, if the scope is on an EQ mount, whether the eyepiece would be held securely enough at some of the angles that the diagonal might find itself at

But as long as the way this works is known about, the choice is an informed one

Well it's always worth being careful, I think I only used it with a 24mm Panoptic and it was fine. It's a balance between how firm it is clamped vs how easy it is to remove (obviously!) but if you want to be sure, a quick nip up on the screws before clamping in the 2" diagonal will do the trick.

[Peter Drew]

On 07/10/2017 at 18:58, Stu said:

Yep, that's the same one, so I don't think you can get any shorter than that.

Oh yes you can , provided that they are obtainable separately, the SW low profile Crayford focuser has a 2" to 1.25" adaptor that has a shoulder around 1mm wide. The adaptor has scantling cuts which grip the eyepiece nicely without spoiling the nosepiece.    

[Stu]

Touché  

Or how about a nice FT which seems to have no shoulder at all!

https://www.firstlightoptics.com/adapters/starlight-instruments-low-profile-eyepiece-adapter.html

[wookie1965]

On 10/7/2017 at 18:58, Stu said:

Yep, that's the same one, so I don't think you can get any shorter than that.

Spoke to FLO my adaptor has a shoulder length of a tad over 8 mm so with this I will have an extra 7 mm of inward focus. Martin at FLO said if I have any problems I can just send the adaptor back so fingers crossed it works I can look for a 4/4.5 mm  eyepiece. Thank you all for your input much appreciated.

[wookie1965]

20 hours ago, Peter Drew said:

Oh yes you can , provided that they are obtainable separately, the SW low profile Crayford focuser has a 2" to 1.25" adaptor that has a shoulder around 1mm wide. The adaptor has scantling cuts which grip the eyepiece nicely without spoiling the nosepiece.    

I dont know how to get the adaptor and the whole focuser wont fit the Tal, but I suspect that you know that.

[wookie1965]

Well looks like I am going to have to cut a slot in my diagonal to make this fit I have about 8.5mm to play with before the compression ring.