Collimating Skywatcher Heritage 76p mini Dob

[Barry-W-Fenner]

34 minutes ago, Alan64 said:

One thing that I've learned over time is that if you don't push the magnification up then you will never know how truly capable a telescope may be in fact, and in showing the user that which few people have ever seen.  Never say never.  That applies to all telescopes, including your 200P.

I recently got this refractive equivalent to your nephew's reflector...

 

...a 70mm f4.3 achromat, also with a 300mm focal-length.  I haven't pushed it to its limits quite yet, as I've got to blacken and flock it first, but I do have high hopes, high-powered hopes, and when I insert the eyepiece/barlow equivalent of a 1.5mm(200x) into it.

That is a very interesting read. So with a 70mm x 300mm focal you are hoping to achieve 200x mag - I have tried to view Jupiter through my 200p with my 5.5mm BST  so 220ish mag and it is very blurry Is there a reason for this? It is considerably clearer with my 8mm BST

 

Thank you

[DaveL59]

I think EP choice will also come down to how easy it'll be to track objects at high mag with the scope. I don't know that model but the NG I have is without slo-mo controls and it is quite difficult to stay on target given the movement isn't as smooth as I'd like. But then I rarely use it as I prefer the EQ setups I have for more than a quick squint  Did make me think tho if its possible to retro-fit something as the original intention was as an entry setup for my daughter+grandaughter and I think they'd soon get frustrated at anything more than low power viewing. I did add an RDF and get a 20-something and 6.3mm plossl set to improve the viewing use tho as the stock ones were pretty poor.

[Barry-W-Fenner]

2 minutes ago, DaveL59 said:

I think EP choice will also come down to how easy it'll be to track objects at high mag with the scope. I don't know that model but the NG I have is without slo-mo controls and it is quite difficult to stay on target given the movement isn't as smooth as I'd like. But then I rarely use it as I prefer the EQ setups I have for more than a quick squint  Did make me think tho if its possible to retro-fit something as the original intention was as an entry setup for my daughter+grandaughter and I think they'd soon get frustrated at anything more than low power viewing. I did add an RDF and get a 20-something and 6.3mm plossl set to improve the viewing use tho as the stock ones were pretty poor.

Very true, Tracking objects at high mag can be quite changeling, I am quite fortunate in the sense that I seem to be pretty good at following an object at high mag. I can stay on shooting stars and quick moving objects also at medium power.

I am not much good at collimating though as you can all tell by this thread 🙂🙂

 

Baz

 

[DaveL59]

23 minutes ago, Barry-W-Fenner said:

I am not much good at collimating though as you can all tell by this thread 🙂🙂

 

Baz

 

tis a learning process for sure but as the old saying goes, practise makes... it does get easier after a few goes but for sure can try your patience  

[Alan64]

Per the old measurements, your 200P is capable of at least 50x per inch.  Your telescope is an 8"...

8" x 50x = 400x

That's the standard for Newtonians, 50x per inch before image-breakdown.  But that is only possible under ideal atmospheric seeing conditions.  Also, the collimation must be spot-on.  Any telescope has to work harder at the higher and highest powers, therefore everything must be in order.  Fine refractors, however, are known to reach 100x per inch.  Under ideal atmospheric seeing conditions, my 4" refractor can reach 400x, but it would need to be on a motorised mount for a good look-see at whichever object I'd be observing at the time; most likely the Trapezium within the Orion nebula, at this time of year.  The eyepieces and barlows also need to be of better quality.  

If you want to see what few people have ever seen, you're going to have to embrace, love, collimating; obsess over it even.

When the planets come round again in a couple of years or so, you're going to want to see those at the higher powers.  I guarantee it, and for that you may want a variable-polariser...

Edited January 17, 2020 by Alan64

[Alan64]

1 hour ago, Barry-W-Fenner said:

That is a very interesting read. So with a 70mm x 300mm focal you are hoping to achieve 200x mag - I have tried to view Jupiter through my 200p with my 5.5mm BST  so 220ish mag and it is very blurry Is there a reason for this? It is considerably clearer with my 8mm BST

 

Thank you

I had this 70mm f/13 achromat...

...up to 225x one night, aimed at Polaris, the north star.  I could still make out the star's Airy disc, and its first and subsequent diffraction-rings; not quite as sharply as at 150x, but it was certainly not so-called "empty magnification", not at all.

It can be the atmosphere, and the state of the telescope's collimation, in keeping you from making good, practical use of the 5.5mm(218x).  We are at the mercy of the atmosphere, but we don't have to be at the mercy of a telescope's level of collimation.  

Edited January 17, 2020 by Alan64

[Barry-W-Fenner]

14 minutes ago, Alan64 said:

Per the old measurements, your 200P is capable of at least 50x per inch.  Your telescope is an 8"...

8" x 50x = 400x

That's the standard for Newtonians, 50x per inch before image-breakdown.  But that is only possible under ideal atmospheric seeing conditions.  Also, the collimation must be spot-on.  Any telescope has to work harder at the higher and highest powers, therefore everything must be in order.  Fine refractors, however, are known to reach 100x per inch.  Under ideal atmospheric seeing conditions, my 4" refractor can reach 400x, but it would need to be on a motorised mount for a good look-see at whichever object I'd be observing at the time; most likely the Trapezium within the Orion nebula, at this time of year.  The eyepieces and barlows also need to be of better quality.  

If you want to see what few people have ever seen, you're going to have to embrace, love, collimating; obsess over it even.

When the planets come round again in a couple of years or so, you're going to want to see those at the higher powers.  I guarantee it, and for that you may want a variable-polariser...

Please dont talk to me about collimation Alan, I cant take anymore 🙂🙂🙂  Seriously though that's impressive, I imagine your collimation needs to be on point to achieve 400!

Variable-polariser, What is this sorcery you speak of! Is it a lens that will stack in an eye piece to improve visual detail? 

Baz

[Barry-W-Fenner]

15 minutes ago, Alan64 said:

I had this 70mm f/13 achromat...

...up to 225x one night, aimed at Polaris, the north star.  I could still make out the star's Airy disc, and its first and subsequent diffraction-rings; not quite as sharply as at 150x, but it was certainly not so-called "empty magnification", not at all.

Impressive, You achieved high mag and retained the image detail!

 

Baz

[Alan64]

Just now, Barry-W-Fenner said:

Please dont talk to me about collimation Alan, I cant take anymore 🙂🙂🙂  Seriously though that's impressive, I imagine your collimation needs to be on point to achieve 400!

Variable-polariser, What is this sorcery you speak of! Is it a lens that will stack in an eye piece to improve visual detail? 

Baz

I'm afraid that the importance of a spot-on collimation cannot be over-emphasised.  Do you know what a drill-sergeant is? 

This, my own variable-polariser...

It simply dims down the light collected by the objective of the telescope.  You still get the resolution of an 8", but there are times when you need to dim it down a bit.  With my 6" f/5, the v-p eliminates the diffraction-effects of the secondary spider-vanes...

Mars through my 6", during its last opposition, before and after...

It also helps to detect the Moon-like phases of Venus.  I don't think that Saturn would benefit from it, however.

[Barry-W-Fenner]

23 minutes ago, Alan64 said:

I'm afraid that the importance of a spot-on collimation cannot be over-emphasised.  Do you know what a drill-sergeant is? 

This, my own variable-polariser...

It simply dims down the light collected by the objective of the telescope.  You still get the resolution of an 8", but there are times when you need to dim it down a bit.  With my 6" f/5, the v-p eliminates the diffraction-effects of the secondary spider-vanes...

Mars through my 6", during its last opposition, before and after...

It also helps to detect the Moon-like phases of Venus.  I don't think that Saturn would benefit from it, however.

Would you recommend purchasing a more expensive one of these? Or can

Edited January 17, 2020 by Barry-W-Fenner
Mistake...

[Barry-W-Fenner]

Would you recommend a more expensive V-P. Will a cheaper one perform as well?

[Alan64]

Just now, Barry-W-Fenner said:

Would you recommend a more expensive V-P. Will a cheaper one perform as well?

That, sir, is an excellent question.  I am impressed.  You wouldn't want a Lumicon?

https://www.robtics.nl/product_info.php?products_id=4993&pID=4993&language=en

That one is regarded as the finest on the planet.  My Orion(of California) v-p was made in Japan, too, many years ago.

But there are economical alternatives.  House/Generic brands...

https://www.firstlightoptics.com/moon-neutral-density-filters/astro-essentials-variable-polarising-moon-filter.html

https://www.365astronomy.com/365astronomy-variable-polarising-filter-1.25-inch.html

https://www.rothervalleyoptics.co.uk/ovl-variable-polarising-filters.html

Name-brands...

https://www.rothervalleyoptics.co.uk/antares-variable-polarising-filter-125.html

https://www.rothervalleyoptics.co.uk/celestron-variable-polarizing-filter-125.html ...new product

Two of the these GSO filters to purchase and to screw together for a v-p... https://www.365astronomy.com/Polarisation-filter-with-30-transmission-level-1.25-inch-M28-5X0.6.html

Orion(of California) still offers a v-p, but it's not made in Japan as my Orion was many years ago.

Per your question as to the performance of a cheaper one, I cannot say.  

[Barry-W-Fenner]

20 minutes ago, Alan64 said:

You wouldn't want a Lumicon?

I would love the Lumicom model. However funds are a little on the tight side this soon after xmas. I was lucky to get my dew shield this week 🙂

Thanks for the comprehensive list of filters, I will most likely give the FLO astro filter a go at pay day!

Baz

 

[Alan64]

10 minutes ago, Barry-W-Fenner said:

I would love the Lumicom model. However funds are a little on the tight side this soon after xmas. I was lucky to get my dew shield this week 🙂

Thanks for the comprehensive list of filters, I will most likely give the FLO astro filter a go at pay day!

Baz

 

A variable-polariser is only good for what was discussed; specific, and of limited use.  I would go with the 1.25".   

Edited January 17, 2020 by Alan64

[Barry-W-Fenner]

Hi Alan

Took your advice and stuck the x2 Barlow with the 5.5mm eye piece in the 200p lined up venue and got a great view. I thought this would be an ideal target to ramp up the mag as there is not much

detail to be lost with venus.  Got n excellent blue,yellow,white disc to stud which was great fun and lovely to see.

 

Thanks Alan