barlow/telextender/power mate advice and zoom lens

[DAT]

Hello, looking for some advice on a barlow/powermate/telextender.

Based n the UK in a heavily light polluted area and to be used with either a 150p or 200p reflector telescope. Budget around £100 but willing to go higher if there is a convincing argument!

I have read a fair bit and understand there are pros and cons to each. I am basically considering one to supplement a zoom eyepiece yet to be bought (8mm-24mm stellalyra made by gso). So mainly to reach higher magnifications to see planets and split stars. 

However, I also have a few a low magnification ep (24mm) and will also be purchasing a 30mm or 32mm.

I understand I need to avoid "doubling up" on eps I already have and would like to make one solid investment that that would be suitable  to use with what I have/intend to buy. I am also looking for alternative suggestions on zoom eyepieces if someone thinks an alternative combination might be better.

I know a lot of this has been covered but was hopefully looking to condense all the different info into one thread given my situation.

As always, thanks for reading! D

Edited November 20, 2023 by DAT

[bosun21]

A 24mm or 32mm are not high magnification eyepieces. The larger the number on the eyepiece the lower the magnification. The magnification is calculated by dividing the focal length of the telescope by the focal length of the eyepiece. For a 200P say that would be 1000mm so a 32mm would give you 1000/32 = 31.25x. A 10mm eyepiece would give you 1000/10 = 100x. Regarding a barlow/ extender I can recommend the Explore Scientific 2x telextender. It's good quality and fits your budget.

[DAT]

27 minutes ago, bosun21 said:

A 24mm or 32mm are not high magnification eyepieces. The larger the number on the eyepiece the lower the magnification. The magnification is calculated by dividing the focal length of the telescope by the focal length of the eyepiece. For a 200P say that would be 1000mm so a 32mm would give you 1000/32 = 31.25x. A 10mm eyepiece would give you 1000/10 = 100x. Regarding a barlow/ extender I can recommend the Explore Scientific 2x telextender. It's good quality and fits your budget.

regarding high magnification, that was a typo, will try to fix and thanks for the recommendation!

[RT65CB-SWL]

Hi @DAT and welcome to SGL. 

If you want a ‘quality’ planetary zoom, have a look at my signature! 

Seriously, both the TeleVue Nagler 3-6mm and the Svbony SV215 3-8mm are both good quality and build. In terms of operation, the Svbony is smoother in changing focal lengths. I have been an early adopter of both since their initial releases and no regrets buying either.

The only ‘real’ differences I have noted is:

• the field of view: TeleVue is 50^o ~ Svbony is 56^o
• both have the same eye-relief: 10mm.
• both are parfocal throughout the entire range of focal lengths.
• a few hundred pounds in price: TeleVue is £424.00 ~ Svbony is £124.00 [note: prices shown in GBP for reference purposes only].

Edited November 25, 2023 by RT65CB-SWL
restructured layout of text...

[Mr Spock]

If you want something to go with an 8-24, then the ideal would be a x3 extender. The ES x3 is £108. That would give you 8-24 and 2.67-8. A bit over powered at the high end for anything other than double stars, but the range from 2.67 to 24 is complete with no overlap or gaps.

As an alternative the Svbony SV135 7-21mm Zoom has excellent image quality and you could pair that with the Svbony 3-8 or the extender. A x2 would retain the quality of the 7-21 over a range of 3.5-10.5 which has overlap but is a good range for planets. 

There are lots of options!

[Louis D]

I think you'll find a preference over time for an eyepiece swap to get to higher powers rather than swapping out the eyepiece, swapping in the Barlow, and then swapping in the eyepiece into the Barlow and then having to refocus quite a bit with many Barlows.  I'd recommend the Svbony 3-8mm as well.  See my write-up below:

It will probably be going on special sale price during the lead up to the holidays.

[Zermelo]

1 hour ago, Louis D said:

It will probably be going on special sale price during the lead up to the holidays.

There's a Black Friday deal on UK Amazon, £110.49, 12 left.

[Zermelo]

If you really did want to spend up to £100 on a "Barlow", I'd go for a x2 telecentric multiplier like this or this. They have some advantages over the regular Barlow design (there is some discussion and links here).  But if I were you, I'd stick with a cheaper, decent, conventional Barlow like this one.

You could use the Barlow with the Stellalyra 8-24mm, if you are already committed to it, or perhaps have a look at the SV315 (the Svbony 7-21mm mentioned by @Mr Spock above, £42.49 in the sales), which has very good reviews. I am currently testing out an SV125 (9-27mm), with which I'm also impressed.  

Finally, as also suggested above, you could try the SV215 3-8mm planetary zoom unBarlowed, which would give a continuous range of magnifications. It is a very decent item (my own review here), but will set you back a little over the £100, even in the sales.

As has already been said, plenty of options.

[Zermelo]

37 minutes ago, Zermelo said:

There's a Black Friday deal on UK Amazon, £110.49, 12 left.

If you were happy to order from abroad, even cheaper:

https://stargazerslounge.com/topic/412945-svbony-zoom-eps-on-sale/?do=findComment&comment=4433978

 

[DAT]

Thanks for all your replies. I think a telextender would be better suit my situation at the moment because I could use it to amplify the eps I already own, the 8-24 zoom lens is a gift for someone, albeit a gift I have access to...

I see many people are recommending the svbony zoom lens and there is a wealth of reviews out there. I have even found it for sale at £60. Has anyone actually used the stellalyra 8-24? Without being able to comment on the optics as I haven't used either, the only advantage I can see is slight increase in afov and eye relief, the latter being important as I use glasses although we are talking about a 1/2mm difference.

Cannot find much said about the stellalyra zoom except for the orion, which some say is the version of  it sold in the US. I wouldn't mind spending the extra money, but not if it isn't worth it.

[Spile]

A combination of Baader zoom, matching Barlow and a couple of low power 2” wide angle EPs (30mm and 42mm) meets my needs.

[bosun21]

On 21/11/2023 at 05:18, DAT said:

the latter being important as I use glasses although we are talking about a 1/2mm difference.

The Svbony 3-8 mm zoom will not be suitable for you if you wear glasses while observing. 10mm ER isn't large enough IMO. Do you have astigmatism? If yes then the above applies. If not then you can simply achieve focus by using the telescope focuser without wearing your glasses.

Edited November 22, 2023 by bosun21
Typo

[DAT]

2 hours ago, bosun21 said:

The Svbony 3-8 mm zoom will not be suitable for you if you wear glasses while observing. 10mm ER isn't large enough IMO. Do you have astigmatism? If yes then the above applies. If not then you can simply achieve focus by using the telescope focuser without wearing your glasses.

Thanks, I realised that hence the inclination to go for a Barlow . I do have astigmatism 

[Second Time Around]

I've just posted this on another topic:

The amplification factor of a Barlow will vary from eyepiece to eyepiece depending on where the focal plane of the eyepiece is situated.  So the stated amplification factors are only approximate.

The amplification factor also depends on the distance between the Barlow and the eyepiece.  With some 2x Barlows the lens cell can be unscrewed from the tube and screwed into the filter cell of the eyepiece.   This gives an amplification factor of approx 1.5x as posted by RT65CB-SWL.

First Light Optics do their own version (probably identical to branded versions) for only £27.  In fact, they currently have an open box return for £24.  Go to https://www.firstlightoptics.com/barlow-eyepieces/astro-essentials-125-2x-barlow-with-t-thread.html

You can also add an extension tube(s) (£16 each) between such a Barlow to increase the magnification (within reason).  See https://www.firstlightoptics.com/adapters/baader-dt-4-1-31-8mm-nosepiece-extension-18mm-long.html  Each extension tube on the Barlow I linked to above will add about an extra 0.25x amplification. 

Another tip with zoom eyepieces is that if you're after a focal length of say 6mm you'll get a wider field of view if you set your zoom at 9mm with a 1.5x Barlow rather than setting it at 12mm with a 2x Barlow.  This is because most zooms have a wider apparent field of view at the shorter focal lengths.

 

Edited November 22, 2023 by Second Time Around

[bomberbaz]

I will just chip in with my own 2 penneth worth here. 

I get what you @DAT mean when you say a barlow/tele-extender will work with existing glass but it isn't adding as much as you might think, especially when combined with the 8-24 zoom.

Let's assume you wind the 8-24 zoom up to 8mm but want to go further on eg Saturn. So you wind back out to hopefully 16, take it out of focuser and shine head torch onto it to make sure your in the right spot, pop it into the tele-ext, put all back into focuser and refocus and you then pick up where you left off from to wind it all the way back to (8) 4mm. I mean it works, you gain the 4,5,6,7 focal lengths although there are no clicks to tell you where you are on the scale in terms of magnification. I still like it though, but I think the svbony 3-8 zoom will serve you better.

For one if you add a parfocal ring to the barrel of whichever eyepiece needs it (if indeed one is needed), it makes for a seamless changeover with no need to refocus.  You will know you are leaving the 8-24 at the 8mm stop point and starting the 3-8mm zoom at it's 8mm start point, no faffing about with a torch. Plus you get the extra 3mm length and from 8 through to 3 is indicated with clicks, you know where you are as long as you can count clicks😂. These are only small points of difference but the combination of these little points make a world of difference when it's dark and you are out viewing.

Finally some have stated the 3-8 zoom isn't suitable for glasses wearers. This statement can be true but can sometimes be a little misleading because not all people need their glasses for viewing as they move down the range to higher magnification. This is down to the exit pupil shrinking as magnification increases and the effects of astigmatism decreasing with the smaller exit pupil.

I have awful astigmatism, it's plus 6 or more. I do wear either glasses or use a dioptrix when viewing using my dob at lower focal lengths. My 24 and 27 fixed length eyepieces really. Below that the affects of the astigmatism becomes less severe and all but disappear at a 10mm eyepiece equivalent on my apm superzoom which gives a 2.5mm exit pupil.

I do not use any vision correction on eyepiece below the 24, I accept the slightly less than perfect stars and learn to view with it. In fairness I go from 24mm to 15mm which is a 3mm exit pupil, it isn't perfect but it isn't awful either.

With my 3-8 svbony zoom super high power (+210 and up) there is nothing in terms of  image degradation. So you  may be able to use a svbony 3-8 and indeed suspect you will find it perfect without your glasses like me.  I also feel you would find it a far better addition to the eyepiece case than a tele-ext or barlow for the reasons laid out above.  

HTH

Steve

 

[DAT]

2 hours ago, bomberbaz said:

I will just chip in with my own 2 penneth worth here. 

I get what you @DAT mean when you say a barlow/tele-extender will work with existing glass but it isn't adding as much as you might think, especially when combined with the 8-24 zoom.

Let's assume you wind the 8-24 zoom up to 8mm but want to go further on eg Saturn. So you wind back out to hopefully 16, take it out of focuser and shine head torch onto it to make sure your in the right spot, pop it into the tele-ext, put all back into focuser and refocus and you then pick up where you left off from to wind it all the way back to (8) 4mm. I mean it works, you gain the 4,5,6,7 focal lengths although there are no clicks to tell you where you are on the scale in terms of magnification. I still like it though, but I think the svbony 3-8 zoom will serve you better.

For one if you add a parfocal ring to the barrel of whichever eyepiece needs it (if indeed one is needed), it makes for a seamless changeover with no need to refocus.  You will know you are leaving the 8-24 at the 8mm stop point and starting the 3-8mm zoom at it's 8mm start point, no faffing about with a torch. Plus you get the extra 3mm length and from 8 through to 3 is indicated with clicks, you know where you are as long as you can count clicks😂. These are only small points of difference but the combination of these little points make a world of difference when it's dark and you are out viewing.

Finally some have stated the 3-8 zoom isn't suitable for glasses wearers. This statement can be true but can sometimes be a little misleading because not all people need their glasses for viewing as they move down the range to higher magnification. This is down to the exit pupil shrinking as magnification increases and the effects of astigmatism decreasing with the smaller exit pupil.

I have awful astigmatism, it's plus 6 or more. I do wear either glasses or use a dioptrix when viewing using my dob at lower focal lengths. My 24 and 27 fixed length eyepieces really. Below that the affects of the astigmatism becomes less severe and all but disappear at a 10mm eyepiece equivalent on my apm superzoom which gives a 2.5mm exit pupil.

I do not use any vision correction on eyepiece below the 24, I accept the slightly less than perfect stars and learn to view with it. In fairness I go from 24mm to 15mm which is a 3mm exit pupil, it isn't perfect but it isn't awful either.

With my 3-8 svbony zoom super high power (+210 and up) there is nothing in terms of  image degradation. So you  may be able to use a svbony 3-8 and indeed suspect you will find it perfect without your glasses like me.  I also feel you would find it a far better addition to the eyepiece case than a tele-ext or barlow for the reasons laid out above.  

HTH

Steve

 

Thanks, make sense but also makes my choice harder. I think I should try one first if I can get to a local astronomy club and see for my self.

Have you by any chance used the Stellalyra zoom and if so, is it worth the extra cash?

2 hours ago, bomberbaz said:

I will just chip in with my own 2 penneth worth here. 

I get what you @DAT mean when you say a barlow/tele-extender will work with existing glass but it isn't adding as much as you might think, especially when combined with the 8-24 zoom.

Let's assume you wind the 8-24 zoom up to 8mm but want to go further on eg Saturn. So you wind back out to hopefully 16, take it out of focuser and shine head torch onto it to make sure your in the right spot, pop it into the tele-ext, put all back into focuser and refocus and you then pick up where you left off from to wind it all the way back to (8) 4mm. I mean it works, you gain the 4,5,6,7 focal lengths although there are no clicks to tell you where you are on the scale in terms of magnification. I still like it though, but I think the svbony 3

[bomberbaz]

34 minutes ago, DAT said:

Thanks, make sense but also makes my choice harder. I think I should try one first if I can get to a local astronomy club and see for my self.

Have you by any chance used the Stellalyra zoom and if so, is it worth the extra cash?

I haven't no, but I believe it will be at least equal optically to the baader 8-24 and I find that a nice bit of kit to use. 

I have 5 zooms in total and find zooms in general are vastly under rated. You do get better quality the more you pay as a rule of thumb but there are some variations to this. The svbony 7-21 is a perfect example.  

If you can get the use of a svbony 3-8 zoom to test I think you would be onto a winner.

Amazon allow you to return within a given time period, no questions asked, might be worth a consideration. 

[bomberbaz]

1 hour ago, DAT said:

Thanks, make sense but also makes my choice harder. I think I should try one first if I can get to a local astronomy club and see for my self.

Have you by any chance used the Stellalyra zoom and if so, is it worth the extra cash?

I have just checked the specs on that eyepiece, it appears mechanically they are likely identical to other zooms in the same bracket. 

In terms of glass which tbf, is where things really matter it appears very good in using 5 lanthanum lens out of a total of 8. 

FYI the pentax zoom comes in at over 400 quid with seemingly very similar specs. 

My understanding is this is freebie! If that's the case I would be most happy 😊. 

Edited November 22, 2023 by bomberbaz

[Chandra]

As a user of the SVBony 3-8mm zoom, I join those who recommend it for planetary observation due to quality and comfort... although in my case I do not suffer from astigmatism but hyperopia, so I do not have your problem with eye relief... And yes, 10mm is a low Er if you must use the glasses, so you should be able to try it before you buy...

[John]

That's my recommendation as well:

low power / wide field fixed focal length + mid-range 8-24 zoom + Svbony 3-8 zoom

Although I put these together as a "travel / outreach" set I seem to be quite happy using them as my regular eyepieces quite frequently 🙄

[DAT]

Thank you everyone for your help, insights are much appreciated. I have made the wrong decisions before and am keen to spend my money wisely now

 

[Ricochet]

On 21/11/2023 at 05:18, DAT said:

Thanks for all your replies. I think a telextender would be better suit my situation at the moment because I could use it to amplify the eps I already own, the 8-24 zoom lens is a gift for someone, albeit a gift I have access to...

Given this, which eyepieces do you currently own? In my opinion zoom eyepieces work best when you need that fine granularity for high power observing, but are not so useful at low and mid powers where you don't need anything closer than root 2 changes in focal length. My (f6) grab and go setup has only three eyepieces; a 3-6mm zoom, a 13mm and a 24mm (approx 2X steps for mid/low powers). If you already have something to cover the mid power then the 3-8mm zoom most people are suggesting might still be the best option so long as your astigmatism is mild enough to get away with not using glasses at the resulting exit pupils. Assuming your scopes are the f5 versions then the 3-8mm zoom will result in exit pupils between 0.6 and 1.6mm. Reading from the Televue graph below if you have less than 1.5 dioptres of astigmatism you should be OK to use the full range of the 3-8mm zoom without needing your glasses.

Televue: Determining When To Use Eyeglasses
Televue: DIOPTRX

[bomberbaz]

1 hour ago, Ricochet said:

. If you already have something to cover the mid power then the 3-8mm zoom most people are suggesting might still be the best option so long as your astigmatism is mild enough to get away with not using glasses at the resulting exit pupils. Assuming your scopes are the f5 versions then the 3-8mm zoom will result in exit pupils between 0.6 and 1.6mm. Reading from the Televue graph below if you have less than 1.5 dioptres of astigmatism you should be OK to use the full range of the 3-8mm zoom without needing your glasses.

Televue: Determining When To Use Eyeglasses
Televue: DIOPTRX

I have seen this diagram before but I assume it is more rule of thumb than hard fact.

If it were the latter then I should always wear glasses or some other correction and that simply isn't the case.

[DAT]

23 hours ago, Ricochet said:

Given this, which eyepieces do you currently own? In my opinion zoom eyepieces work best when you need that fine granularity for high power observing, but are not so useful at low and mid powers where you don't need anything closer than root 2 changes in focal length. My (f6) grab and go setup has only three eyepieces; a 3-6mm zoom, a 13mm and a 24mm (approx 2X steps for mid/low powers). If you already have something to cover the mid power then the 3-8mm zoom most people are suggesting might still be the best option so long as your astigmatism is mild enough to get away with not using glasses at the resulting exit pupils. Assuming your scopes are the f5 versions then the 3-8mm zoom will result in exit pupils between 0.6 and 1.6mm. Reading from the Televue graph below if you have less than 1.5 dioptres of astigmatism you should be OK to use the full range of the 3-8mm zoom without needing your glasses.

Televue: Determining When To Use Eyeglasses
Televue: DIOPTRX

Currently have a 5mm, 11mm and 24mm. The idea of the zoom eyepiece was as a “gift” that I could use….The 3 x telextender will be nice to use with the 24 mm as quality on the 5mm is inconsistent depending on conditions. I suppose it’s trial and error because there are loads of options , the maths of it all is quite interesting!!!

[Chandra]

15 hours ago, DAT said:

Currently have a 5mm, 11mm and 24mm. The idea of the zoom eyepiece was as a “gift” that I could use….The 3 x telextender will be nice to use with the 24 mm as quality on the 5mm is inconsistent depending on conditions. I suppose it’s trial and error because there are loads of options , the maths of it all is quite interesting!!!

The TX 3x with your 24mm eyepiece would give you around 94x or 125x (depending on whether it is the 150P or 200P reflector), while your 5mm eyepiece gives you 150x and 200x respectively, these are not very similar magnifications and exit pupils. On the other hand, it must be considered that Telextenders sometimes cause intrafocus problems, especially with equipment with a short focus path as is the case with Newtonian reflectors. If you feel that your current 5mm is not providing you with enough quality views, I still think that the most suitable option would be the zoom, as long as you can have one to compare it with your astigmatism, and, if not, I think that I would opt for one or two eyepieces with a low focal length and high Er, such as those from TS Optics (HR Planetary or N-ED), Omegon Cronus WA, Explore Scientific LER 52º and others.