Eyepiece help please

[Astro_Nic]

So I think I'm going to purchase a 14 inch dob - f 4.6, FL 1,600mm, PV 1/10.

Need some eyepieces etc to go with it.  I thought the following might be a good place to start, but open to suggestions of alternatives.  Interest is DSOs but also some planetary, nebula etc:

• 9mm ES 100 degree FOV 2 inch - this would give me 170 x magnification;
• 30mm APM UFF 2 inch - this would give me 53 degree magnification;
• 2x Televue powermate 2 inch - this would then increase the above magnification options to 340, 170, 106 and 53;
• I could replace the the ES with the 9mm Televue Nagler 82 degree FOV as it is a similar price but seems to be much more easily available - how would these two compare?
• I could possible add another ES 82 degree field or similarly priced eyepiece if you feel I need an additional one;
• Moon filter - suggestions please?
• Nebula filter - ES CLS 
• I don't wear glasses.  Wife does but only long sighted so eye relief shouldn't be an issue.

Please could you advise on the above?  

Many thanks!

Edited August 31, 2021 by Cornelius Varley
formatting corrected for colour

[John]

I've asked the moderators to change the colour of the text in your post - it comes out as grey for me and hard to read !

My only comment would be on the filter for nebulae. A UHC or O-III (ideally both) would be a much more effective choice than a CLS. You will want a 2 inch filter. Astronomik or Tele Vue have excellent UHC and O-III filters.

Personally I don't use a moon filter even with my 12 inch dobsonian but quite a few folks do find them useful.

[Cornelius Varley]

Colour corrected.

[John]

9 minutes ago, Cornelius Varley said:

Colour corrected.

Many thanks

[Louis D]

4 hours ago, Astro_Nic said:

9mm ES 100 degree FOV 2 inch - this would give me 170 x magnification;

Don't overlook the 9mm APM XWA 100°.  It's lighter and cheaper than the ES alternative, and most reports rank it as just as good if not better.

4 hours ago, Astro_Nic said:

30mm APM UFF 2 inch - this would give me 53 x magnification;

Excellent choice.  My preferred eyepiece at that focal length.  The ES-82 is wider, but has issues with CAEP (Chromatic Aberration of the Exit Pupil) aka, ring of fire at the edge.

4 hours ago, Astro_Nic said:

2x Televue powermate 2 inch - this would then increase the above magnification options to 340, 170, 106 and 53

You'll find yourself either leaving it in the focuser for extended observing periods or removing it.  PMs and Barlows are just too clunky to be swapping in and out regularly.  I would spend the money on dedicated eyepieces, myself.  That, and you'll have a really long optics train hanging off your focuser.  I would probably recommend 13mm and 4.77mm APM XWA 100° to fill the power gaps instead.  The latter is 110° which will be really helpful at high powers with a nondriven Dob.

4 hours ago, Astro_Nic said:

Moon filter - suggestions please?

Pick up a cheap moon filter off of ebay or similar if you feel the need.

4 hours ago, Astro_Nic said:

Nebula filter - ES CLS

Pick up a quality OIII first and UHC second.  Don't go cheap on either one.  Astronomik, Lumicon, and several others are quite good.

4 hours ago, Astro_Nic said:

I don't wear glasses.  Wife does but only long sighted so eye relief shouldn't be an issue.

As long as neither of you has astigmatism (CYL correction), you'll both be fine without eyeglasses at the eyepiece.  You can just focus out the distance correction.  Depending on how strong the prescription is, the field stop may get a bit fuzzy because you're moving the image circle away from it to compensate for the observer's eye.

[Astro_Nic]

14 hours ago, Louis D said:

Don't overlook the 9mm APM XWA 100°.  It's lighter and cheaper than the ES alternative, and most reports rank it as just as good if not better.

Excellent choice.  My preferred eyepiece at that focal length.  The ES-82 is wider, but has issues with CAEP (Chromatic Aberration of the Exit Pupil) aka, ring of fire at the edge.

You'll find yourself either leaving it in the focuser for extended observing periods or removing it.  PMs and Barlows are just too clunky to be swapping in and out regularly.  I would spend the money on dedicated eyepieces, myself.  That, and you'll have a really long optics train hanging off your focuser.  I would probably recommend 13mm and 4.77mm APM XWA 100° to fill the power gaps instead.  The latter is 110° which will be really helpful at high powers with a nondriven Dob.

Pick up a cheap moon filter off of ebay or similar if you feel the need.

Pick up a quality OIII first and UHC second.  Don't go cheap on either one.  Astronomik, Lumicon, and several others are quite good.

As long as neither of you has astigmatism (CYL correction), you'll both be fine without eyeglasses at the eyepiece.  You can just focus out the distance correction.  Depending on how strong the prescription is, the field stop may get a bit fuzzy because you're moving the image circle away from it to compensate for the observer's eye.

Thanks - will take a look at the APM 9mm

It's weird as all the beginner guides say get barlows to reduce number of eyepieces, yet all the advice seems to be to not to bother......

So say I get all 100 degree APMs - what targets would I use for each of the sizes - 5mm, 9mm, 13mm and 30mm ?  Is that a good spread?  340x, 170x, 123x, 53x ?

What's the main difference between OIII and UHC filters?  Do you use both at once or just one at a time?

Are the APMs suitable for binoviewers if I went that way?  

 

Thanks!

[Louis D]

3 hours ago, Astro_Nic said:

It's weird as all the beginner guides say get barlows to reduce number of eyepieces, yet all the advice seems to be to not to bother......

Written by people who haven't spent a good chunk of their lives out under the stars, I suspect.  I tend to leave mine in the focuser the entire night when I want to use all of my eyepieces at double their normal magnification, which isn't very often.

3 hours ago, Astro_Nic said:

So say I get all 100 degree APMs - what targets would I use for each of the sizes - 5mm, 9mm, 13mm and 30mm ?  Is that a good spread?  340x, 170x, 123x, 53x ?

25x to 50x is good for very large open star clusters, solar system conjunctions, typical solar observing (with safe solar filter) sweeping rich star fields, and detecting comets.

50x to 100x is good for large open star clusters, emission nebula, the whole moon at once, and large galaxies from dark sites.

100x to 150x is good for small open star clusters, planets on nights of average seeing, smaller galaxies from dark sites, viewing the moon in large swaths, and splitting many double star systems.

150x to 200x is good for planets on nights of above average seeing, planetary nebula, lunar details, starting to resolve globular clusters, and splitting tighter double stars.

200x+ is good for planets on nights of exceptional seeing, bright planetary nebula details, challenging lunar details, interacting galaxies from dark sites, fully resolving globular clusters, and splitting the tightest double stars.

I'm sure I missed someone's favorite type of observing in there.  That, and folks will argue about what magnification works best for each.  It's nice to have an assortment of eyepieces to try out to match the seeing conditions with the object at hand.

3 hours ago, Astro_Nic said:

What's the main difference between OIII and UHC filters?  Do you use both at once or just one at a time?

OIII only pass the two oxygen emission lines while UHC filters add one or both hydrogen emission lines.  As a result, the OIII filter has a narrower passband and a higher rejection of light pollution.  However, some emission nebula just don't emit much in the oxygen lines, so the UHC or even an Hß filter comes into play.

You don't use them together.  It's either one or the other.  The OIII is a subset of the UHC.  The OIII and Hß are mutually exclusive.

A lot of folks like the Baader Contrast Booster on planets and other objects to make it easier to pick out low contrast details, but I've not tried one personally.  I've had some luck with an 80a filter on Jupiter to bring out the Great Red Spot better.

3 hours ago, Astro_Nic said:

Are the APMs suitable for binoviewers if I went that way?

Probably not.  They're heavy and fat.  You might not be able to get two of them close enough together for your IPD.  That, and your nose or at least its bridge between your eyes might not fit between the eyepieces, either.  Most folks use smaller, lighter weight eyepieces in their BVs.  Adapted microscope eyepieces can even work quite well I've found.

Also, most folks tend to use lower powered eyepieces with BVs because it's easier to merge their images.  Higher powered eyepieces tend to reveal any slight miscollimation in the BV.  You can always boost the power by adding a Barlow element ahead of the BV.  They also help you to reach focus in Dobs which don't usually have enough in-focus for BVs natively (about 100mm required).

[Astro_Nic]

35 minutes ago, Louis D said:

Written by people who haven't spent a good chunk of their lives out under the stars, I suspect.  I tend to leave mine in the focuser the entire night when I want to use all of my eyepieces at double their normal magnification, which isn't very often.

25x to 50x is good for very large open star clusters, solar system conjunctions, typical solar observing (with safe solar filter) sweeping rich star fields, and detecting comets.

50x to 100x is good for large open star clusters, emission nebula, the whole moon at once, and large galaxies from dark sites.

100x to 150x is good for small open star clusters, planets on nights of average seeing, smaller galaxies from dark sites, viewing the moon in large swaths, and splitting many double star systems.

150x to 200x is good for planets on nights of above average seeing, planetary nebula, lunar details, starting to resolve globular clusters, and splitting tighter double stars.

200x+ is good for planets on nights of exceptional seeing, bright planetary nebula details, challenging lunar details, interacting galaxies from dark sites, fully resolving globular clusters, and splitting the tightest double stars.

I'm sure I missed someone's favorite type of observing in there.  That, and folks will argue about what magnification works best for each.  It's nice to have an assortment of eyepieces to try out to match the seeing conditions with the object at hand.

OIII only pass the two oxygen emission lines while UHC filters add one or both hydrogen emission lines.  As a result, the OIII filter has a narrower passband and a higher rejection of light pollution.  However, some emission nebula just don't emit much in the oxygen lines, so the UHC or even an Hß filter comes into play.

You don't use them together.  It's either one or the other.  The OIII is a subset of the UHC.  The OIII and Hß are mutually exclusive.

A lot of folks like the Baader Contrast Booster on planets and other objects to make it easier to pick out low contrast details, but I've not tried one personally.  I've had some luck with an 80a filter on Jupiter to bring out the Great Red Spot better.

Probably not.  They're heavy and fat.  You might not be able to get two of them close enough together for your IPD.  That, and your nose or at least its bridge between your eyes might not fit between the eyepieces, either.  Most folks use smaller, lighter weight eyepieces in their BVs.  Adapted microscope eyepieces can even work quite well I've found.

Also, most folks tend to use lower powered eyepieces with BVs because it's easier to merge their images.  Higher powered eyepieces tend to reveal any slight miscollimation in the BV.  You can always boost the power by adding a Barlow element ahead of the BV.  They also help you to reach focus in Dobs which don't usually have enough in-focus for BVs natively (about 100mm required).

Thanks very much for your help!

[Astro_Nic]

I guess the Morpheus could be a good binoviewer choice.  In the 17.5 with x2 barlow?

[jetstream]

5 hours ago, Astro_Nic said:

So say I get all 100 degree APMs

Some of us use low power 100 deg eyepieces for filter use and finding galaxies etc, espc in a 14" dob at f4.6. The 9mm APM will be a good higher power galaxy viewer eventhough many use a bit different spec eyepiece for this observing (and many dont...) The Delos/Pentax XW are very highly recommended for this and also provide sharper views on the moon/planets than the 82/100 deg EP's (IMHO).

The 20mm APM is hard to beat for a low power eyepiece in this planned scope- throw in a couple of Delos and all set- I love spending others money lol!

ps a top UHC/OIII will be a huge benefit- Astronomik or new Televue IMHO.

[RT65CB-SWL]

I don't think I have enough experience, but I will reply/contribute  lanyway...

On 31/08/2021 at 15:47, Astro_Nic said:

• I could replace the the ES with the 9mm Televue Nagler 82 degree FOV as it is a similar price but seems to be much more easily available - how would these two compare?
• I could possible add another ES 82 degree field or similarly priced eyepiece if you feel I need an additional one;

Many SGL'ers are TeleVue fans, myself included... as per the two Nagler's in my signature [image below], I have a few others which are listed below...

• Nagler 3-6mm zoom
• Radain 6mm
• Plossl 15, 13 & 8mm

My 'one-to-many' TeleVue 13mm e/p's...

left: 13mm 'smoothside' Plossl      centre: 13mm Nagler Type 1      right: 13mm Nagler Type 6      

I have not used or owned any Explore Scientic e/p's... so no comment... 

...but I do like their boxes.

 

On 31/08/2021 at 15:47, Astro_Nic said:

• Moon filter - suggestions please?

I prefer to use a variable polarising filter.

 

On 31/08/2021 at 15:47, Astro_Nic said:

• Nebula filter - ES CLS 

I tend to prefer the Exploure Scientic UHC over their CLS and their OIII is good for visual in my opinion if you are on a budget.
Another contender is the Baader Plantetarium Neodymium. This is my 'Swiss-Army' knife filter for most of the time.

Edited September 5, 2021 by Philip R

[rl]

I have what I suspect is the exact type of scope you are purchasing...and it's a stonking piece of kit. If you're planning on moving it often, some form of scope buggy might be in order. 

I don't see any mention of a coma corrector....I find a Paracorr makes a very useful improvement at focal lengths 13mm and above. It is of course a personal thing how much coma you can cope with, but once you've dropped a massive wedge (not literally..)on a 1/10 mirror and a bunch of top-notch eyepieces to match, you find yourself looking out for distortions so it seems a shame to compromise the overall magnificence of the view! As the cliche goes..Other coma correctors are available...but the Paracorr is hard to beat for operational convenience. But try without first and see how you get on.  Once you're up above *150 magnification the coma gets small enough to ignore, and I've had the occasional suspicion it detracts from the detail on planets even though it's supposed not to. Taking it out leads to balance issues assuming you balanced the scope in the first place for a Paracorr plus a Nirvana 28..

If you do go for the Paracorr then you might want to re-run your sums to account for the 15% extra magnification. 

I've several examples of non-Televue 100 degree eyepieces..including the ES 9mm and the APM 13mm, 3.5mm Myriad. My overall totally non-scientific impression is that  APM comes closest to matching the real TV deal for levels of contrast. I prefer the 10mm Ethos to the 9mm ES. I actually spent a long time waiting for a secondhand E13 to turn up at  under 400 quid and gave up when a APM 13mm came up for less than half that price. I've not been disappointed. 

I'm using a UWAN 28mm as my lowest-power finding eyepiece. Lots of field, but the sky is a bit bright in average UK skies to utilise a 7mm exit pupil effectively. The Ethos 21 is more useful to study objects with. The APM 20mm might well be worth a punt given the stratospheric price of the E21. 

[Jiggy 67]

I can see where @Louis D is coming from with the filters but I disagree (as we all do sometimes 😀) The UHC has a wider band pass and so let’s in more light across the spectrum which means it’s better for a wider range of nebulae, I would get an Astronomik UHC first followed by the Astronomik OIII next. The OIII is a narrower band pass and more specialized to the oxygen end of the spectrum. It can dim your target significantly, though you will have the aperture to compensate for that to some extent 

[Voyager 3]

7 hours ago, Astro_Nic said:

Thanks - will take a look at the APM 9mm

It's weird as all the beginner guides say get barlows to reduce number of eyepieces, yet all the advice seems to be to not to bother......

So say I get all 100 degree APMs - what targets would I use for each of the sizes - 5mm, 9mm, 13mm and 30mm ?  Is that a good spread?  340x, 170x, 123x, 53x ?

What's the main difference between OIII and UHC filters?  Do you use both at once or just one at a time?

Are the APMs suitable for binoviewers if I went that way?  

 

Thanks!

You will be using a Paracorr II / paracorr for the best correction to use with 100° stuff . It adds 1.15× to the FL/ Focal ratio . 

 

So I take the FL as 1878 . 

Here is your spread with 30mm ( UFF )-13mm-9mm-4.75mm( really a 4.75mm approximately and not a 5mm ) . The 30mm can be substituted by the 20mm XWA  , if your site is light polluted . 

62× - 144× - 208× - 395×  . 

As you can see this is a good set until you reach the 9mm . It's a really big jump from 9mm to 4.75mm . 

A 6mm Ethos fits right in at 313× , but the 7mm APM XWA will also be a good step up at 268× . 

Now it looks like 

62× - 144× - 208× - 268× - 395× . 

Basically you may still need to fill the gap between 7mm and 4.7mm but it is down the list . A coma corrector like the paracorr II must be your first purchase . This assumes you already have good collimation tools . 

 

[John]

Just on the filters, I was happy with just an O-III (Astronomik) for a couple of years with my 12 inch dob. I have now also added a good UHC filter but the O-III gets much more use and has noticably more "oomph" especially on targets such as the Veil Nebula which is an absolute "must see" with a good sized dobsonian. 

With my 12 inch dob, which has a focal length of 1590mm, my most used eyepieces are 21mm, 13mm, 8mm, 6mm and 4.7mm. All Tele Vue Ethos's.

 

[Astro_Nic]

Wow thanks guys!  But stop spending my money! lol!

I am thinking that the 30mm may have a too large exit pupil and hence be too bright - so looks like a 20mm might be the place to start.

I'm still not sure I understand why not to use a powermate - looks like I can lose two eyepieces then!  Although I get it's a pain to change and also adds weight and length to the eyepiece.....have I just listed the reasons?!  Cheaper though!

Ethos looks the business but I'm not spending that money on my first eyepiece!

Will I ever get the opportunity to use 395x ?  Seems very high......

So do I need a parracor - I do want an awesome view and I am the sort of person to look for problems after spending lots of money!  Type 2?

Have no collimation tools....aaaarrrrggghhh!  What do you recommend?

How do you balance an aluminium dob?  Velcro straps with running wrist weights?  Obviously can't use magnetism and don't want to start drilling into a brand new scope!

 

Thanks!

[rl]

Quote

So do I need a parracor - I do want an awesome view and I am the sort of person to look for problems after spending lots of money!  Type 2?

This question depends a lot on the quality of the eyepieces you buy. 

When I got my first 14" Newt...it was a f/5.7 scope, pretty long by modern standards, so relatively easy on off-axis eyepiece aberrations, or so I thought.  I bought a set of GSO 2" eyepieces being sold as a set by Telescope House...they included a 42mm, 30mm and 26mm 5-element jobbies. The view was awful in all of them...anything further than 50% of the way to the edge was just a seagull/ cross/ chromatic mess of mushy astigmatism with coma. I thought a Paracorr would sort it all out and so bought one..which was disappointment number two. The Paracorr only takes out coma...the view was slightly better but still awful. Certainly not worth spending 200 quid on (2007 prices..). My biggest problems by far were with off-axis astigmatism in the cheap eyepieces. . So in the end I bit the bullet and splashed out on a 13 Ethos, and the 28mm UWAN, and the view was indeed virtually perfect in both. The Paracorr is only really effective once all the other nasties are taken out of the equation.  

I appreciate the Ethos series is stupid money especially post-brexit, but some of the clones do come pretty close. Wide field is really useful in this sort of Dob because it will allow you lots more time to look rather than spending all night nudging the thing. Maybe not 100 degrees..there are some really good 82 options out there. 

Personally I'd get one good low-power eyepiece to start. This will have the worst coma. See if you can live with it first...if you can't then get the Paracorr. I would expect a 20mm eyepiece to see a lot of use so you might as well have it in focus. 

Quote

Will I ever get the opportunity to use 395x ?  Seems very high......

True. It's too high for the vast majority of nights. I find that *200 is a good top whack for a lot of scopes 4" and upwards in average UK conditions just because seeing limits the optical system's performance. You will occasionally need more when the seeing co-operates but an 8mm eyepiece will see a lot of use in the high-power role. I occasionally use 4.7mm (without a paracorr!)

Quote

•  

Have no collimation tools....aaaarrrrggghhh!  What do you recommend?

Good collimation is pretty important. Lasers are very convenient but far from the total answer. I use one for rough alignment and follow up with a Cheshire eyepiece.  We all have our pet methods on this one. There is a whole encyclopaedia of threads about collimation on this site! The good news is that the OO cells hold collimation pretty well. The biggest risk to collimation is knocking the scope as you carry it about. 

Quote

How do you balance an aluminium dob?  Velcro straps with running wrist weights?  Obviously can't use magnetism and don't want to start drilling into a brand new scope!

Truth is my OO VX14 in only perfectly balanced for a 21 Ethos plus paracorr. I rely on the friction brake a lot. At least it tips up rather than down...

I have a couple of weights with strings and cuphooks that can be clipped to the front if I feel like using a 6mm ortho...

Edited September 1, 2021 by rl
spelling

[Louis D]

2 hours ago, Astro_Nic said:

Have no collimation tools....aaaarrrrggghhh!  What do you recommend?

I use a cheshire/sight tube to get the secondary square under the focuser.

I use a laser to get the secondary on the center of the primary.

I use a Rigel Aline to get the primary lined up with the rest of the system.

[Louis D]

2 hours ago, Astro_Nic said:

I'm still not sure I understand why not to use a powermate - looks like I can lose two eyepieces then!  Although I get it's a pain to change and also adds weight and length to the eyepiece.....have I just listed the reasons?!  Cheaper though!

Yes, it can be a useful way to stretch your dollars starting out.  Just be aware of how long things get with a Powermate, Paracorr, and a 100 degree eyepiece all in the focuser at the same time:

Focuser flex could become an issue.  Although as @John has pointed out, they can come in handy for other uses:

[John]

I knew that I would regret posting that pic !

[Jiggy 67]

3 hours ago, John said:

Just on the filters, I was happy with just an O-III (Astronomik) for a couple of years with my 12 inch dob. I have now also added a good UHC filter but the O-III gets much more use and has noticably more "oomph" especially on targets such as the Veil Nebula which is an absolute "must see" with a good sized dobsonian. 

You’re absolutely right John, I’m not saying don’t get an OIII, I definitely would, but I think a UHC is a better introduction to filters. I think if I had started with an OIII I would have been turned off filters for life because it really does need a bit of aperture. I think a UHC is a good way of introducing yourself to narrowband filters 

[Stu]

3 minutes ago, Jiggy 67 said:

You’re absolutely right John, I’m not saying don’t get an OIII, I definitely would, but I think a UHC is a better introduction to filters. I think if I had started with an OIII I would have been turned off filters for life because it really does need a bit of aperture. I think a UHC is a good way of introducing yourself to narrowband filters 

I’m sure we all have different opinions on this but just to say, I’ve used my OIII filter successfully in scopes from 72mm upwards. You do need to be well dark adapted to get the best out of them with smaller apertures but they will still give excellent results.

[Louis D]

27 minutes ago, Jiggy 67 said:

You’re absolutely right John, I’m not saying don’t get an OIII, I definitely would, but I think a UHC is a better introduction to filters. I think if I had started with an OIII I would have been turned off filters for life because it really does need a bit of aperture. I think a UHC is a good way of introducing yourself to narrowband filters 

Not so much aperture as large exit pupil.  Yes, that will mean lower magnification with smaller aperture scopes, but that can be a good thing for large objects like the Veil nebula.

If I had started with my Lumicon UHC, I probably would have written off all nebula filters as "Meh".  Some improvement, but not a dramatic improvement in the view.  The OIII is a "Wow" filter with what it can bring out.  Invisible nebula like the Veil stand out as etched on the sky.  Remove it, and the Veil disappears.

Is the OIII filter right for all emission nebula?  Certainly not.  However, more often than not, it offers a very noticeable improvement in the view.

[Zermelo]

15 hours ago, Jiggy 67 said:

I can see where @Louis D is coming from with the filters but I disagree (as we all do sometimes 😀) The UHC has a wider band pass and so let’s in more light across the spectrum which means it’s better for a wider range of nebulae, I would get an Astronomik UHC first followed by the Astronomik OIII next. The OIII is a narrower band pass and more specialized to the oxygen end of the spectrum. It can dim your target significantly, though you will have the aperture to compensate for that to some extent 

Not quite in the league of the "refractor vs reflector" debates, but this one does have a pedigree, e.g. :

https://stargazerslounge.com/topic/369823-uhc-and-oiii-filters/

https://stargazerslounge.com/topic/370053-one-filter-to-rule-them-all/

 

This resource: https://www.prairieastronomyclub.org/filter-performance-comparisons-for-some-common-nebulae/  has been referenced more than once as a creditable attempt to compare the results of nebula filters on specific DSOs. But take note of the instruments used.

My own experience so far with a 150mm Newtonian under Bortle 4 gives a slight preference for UHC. That might be because it is a different make (Astronomik UHC vs OVL OIII) but I do find the OIII to be too severe on the available light. I think the OP's 14" dob would be a different matter.

 

 

[Astro_Nic]

Thanks.....think the jury is out in all the reviews I've read....half say go UHC and half OIII - only going to start with one for now - maybe flip a coin?!