Questions about Telescope Accessories

[Naten]

I have decided that I'd like to buy a Zhumell Z8 8" dob to complement my AstroMaster LT 60AZ's portability and reliability with a heavier instrument, to ease observation of dimmer things like deep sky objects. However, I have also considered buying a 1.25" Zhumell UHC filter to increase contrast on some fuzzies, but the Z8's included 32mm Plössl is a 2.5-inch sized eyepiece. The Z8 comes with an adapter to fit smaller eyepieces, including the included 9mm 1.25-inch eyepiece. However, I am wondering if the filter can be fitted to the adapter as well, allowing for me to only buy a 1.25-inch UHC filter that I can use on both 2.5" and 1.25" eyepieces.

Next question. Are larger telescopes useful for light polluted skies? I understand that a lightbucket is no substitute for truly dark skies, but would I have an easier time seeing deep sky objects with a Z8, with and without the UHC filter to improve contrast?

Also, is Telescopes Plus a good place to order equipment? Thanks, clear skies.

[Ricochet]

You won't be able to fit both the 1.25" adapter and a 2" eyepiece at the same time and it is unlikely to be threaded for 1.25" filters anyway. It might be threaded for 2" filters which would allow you to use 2" filters with both 1.25" and 2" eyepieces. You wouldn't want to use a 1.25" filter with a 2" ep because the use of a 2" barrel is dictated by the field of view and to block the outer 0.75" will vignette the image. However, a 32mm Plossl is usually found with a 1.25" barrel and so supplying one in a 2" barrel is probably more of a marketing ploy than anything else. 

The Z8 will be a lot more useful than the 60az under all skies. Yes, there will be diminishing returns with larger apertures but to be honest the 60az is really a bit too small and so the difference between the two will be significant. 

I have no experience with US retailers and so I will leave that to others to advise. 

[tony210]

Hi - there are always diminishing returns with increasing aperture and even things like weight ease of set up and time to thermal equilibrium of your scope are important considerations - nonetheless if you are looking at bright targets resolution on objects like planets improves considerably with aperture despite your skies - so not an easy answer - I live with moderately light polluted skies and recently upgraded from an 8 inch RCT to a 12 inch - vast learning curve -took me a year to improve my imaging with a big scope and longer FL and more difficult guiding- would not go bigger - best wishes Tony.

[Dave In Vermont]

Just to help clarify - it's a 2" eyepiece you mean. 2 1/2" doesn't exist.

I'd hold off on getting a UHC until you learn about them and such entities as 'bandwidth' so you can choose the best one for your uses. Narrow-Band Filters - like a UHC - shouldn't be bought based on their price - but on how good they are for your chosen applications.

Best wishes -

Dave

[Naten]

15 hours ago, Dave In Vermont said:

Just to help clarify - it's a 2" eyepiece you mean. 2 1/2" doesn't exist.

I'd hold off on getting a UHC until you learn about them and such entities as 'bandwidth' so you can choose the best one for your uses. Narrow-Band Filters - like a UHC - shouldn't be bought based on their price - but on how good they are for your chosen applications.

Yes, 2" is what I meant. Bandwidth is how large the filter's "allowed" spectrum is, right?

[Naten]

18 hours ago, Ricochet said:

You won't be able to fit both the 1.25" adapter and a 2" eyepiece at the same time and it is unlikely to be threaded for 1.25" filters anyway. It might be threaded for 2" filters which would allow you to use 2" filters with both 1.25" and 2" eyepieces. You wouldn't want to use a 1.25" filter with a 2" ep because the use of a 2" barrel is dictated by the field of view and to block the outer 0.75" will vignette the image. However, a 32mm Plossl is usually found with a 1.25" barrel and so supplying one in a 2" barrel is probably more of a marketing ploy than anything else. 

The Z8 will be a lot more useful than the 60az under all skies. Yes, there will be diminishing returns with larger apertures but to be honest the 60az is really a bit too small and so the difference between the two will be significant. 

Alright, thanks. I misunderstood the adapter: the telescope's eyepiece "tube" is for 2" eyepieces, and the adapter downsizes it, from what I can now understand.

However, for now, I think that I will buy a 1.25" UHC first and then a 40mm 1.25" EP, allowing me to use the filter on my 60AZ (it's surprisingly good at deep sky observations, actually. I've done observations of the Orion Nebula, and it reveals a hazy nebulosity, and splits the Trapezium) and on eyepieces that are in the more common 1.25" size. I plan on buying the 40mm EP before the Z8, so that I can use the 40mm eyepiece with the 1.25" filter, which I could use with the Z8's adapter. Would this be possible?

[John]

In the 1.25" size, a 32mm eyepiece can show as much sky as a 40mm but with a more pleasing 52 degree apparent field as opposed to the rather confined 43 degrees of the 40mm. The exit pupil produced by the 32mm eyepiece when it's used in the 8" F/6 Z8 (exit pupil = disk of light that exits an eyepiece) is more efficient as well because it's a better match for the dilated pupil of the average eye.

 

[Ricochet]

3 hours ago, Naten said:

I plan on buying the 40mm EP before the Z8, so that I can use the 40mm eyepiece with the 1.25" filter, which I could use with the Z8's adapter. Would this be possible?

The filter screws into the eyepiece and then the eyepiece-filter combination slots into the adapter so yes it will work. As John says, the 32mm is probably a better choice as the apparent field of the 40mm will probably feel quite restricted. 

[Louis D]

On 2/20/2017 at 12:08, Naten said:

Also, is Telescopes Plus a good place to order equipment?

I've only ever bought a few Zhumell branded filters from them.  No issues to speak of.  I ordered them and they arrived a few days later.  I don't know about ordering large items from them.

There's a couple of CN threads that seem to give them a thumbs up relative to dob purchases.

[Naten]

On 2/21/2017 at 09:47, John said:

In the 1.25" size, a 32mm eyepiece can show as much sky as a 40mm but with a more pleasing 52 degree apparent field as opposed to the rather confined 43 degrees of the 40mm. The exit pupil produced by the 32mm eyepiece when it's used in the 8" F/6 Z8 (exit pupil = disk of light that exits an eyepiece) is more efficient as well because it's a better match for the dilated pupil of the average eye.

Any eyepieces that you can recommend? Preferably on the cheaper (<50 USD) range, if it's not horrible. Thanks.

[Louis D]

4 minutes ago, Naten said:

Any eyepieces that you can recommend? Preferably on the cheaper (<50 USD) range, if it's not horrible. Thanks.

I have the GSO 32mm Plossl, and it is quite well made with good polish and nice multicoatings.  Views are sharp without ghosting.

[Dave In Vermont]

Plossl's are all-around good eyepieces for those on a budget. The only caution I'd be aware of is eyeglass-wearers may find their eye-relief problematic if you need to wear your glasses while looking through the scope.

Other than this, they're good designs and come in a wide-range of sizes for most everything.

Hope this helps -

Dave

[Louis D]

21 hours ago, Dave In Vermont said:

The only caution I'd be aware of is eyeglass-wearers may find their eye-relief problematic if you need to wear your glasses while looking through the scope.

I can easily use the 32mm, but the 26mm is tight.  The fault with both lies in having the eye lens deeply recessed in the housing.