Getting the most out of my new 8 inch dob

[JJJ]

I finally purchased an 8 inch dob, f/5.9, 1200mm, and am looking for help investing in some eyepieces/filters that will last, match up well with my scope, and allow balance of high power for lunar and planetary viewing and wide view viewing for dso. I also would like to get the most out of my scope and the potential for a 2 inch eyepiece/filters that may cost more but really improve the experience. I do wear glasses for astigmatism so eye relief is an issue.  Not asking much, I know...

I currently have the stock Super 10 & Super 25 wide angle, Sybony 9mm LER 68* uwa, & 6.3mm PLOSSL.  I am awaiting an Es82 14mm LER (which I am very excited for) and Celestron X-CEL LX 2x barlow. 

I'd like to add a good quality high power eyepiece and a good quality low power, wide angle that will last. I'd also really like to see what a 2 inch eyepiece can do vs the 1.25, but don't want to waste money for limited return with my f/5.9, 1200m.  

Lastly, I'd love to see more detail in nebula and other dsos but am unsure on value in filters vs quality eyepieces. 

My budget is around $500, and I'm in no rush.

What would you recommend, buy first, wait on, not recommend? What are your eyepieces you wouldn't do without?

Clear skies!

[Geoff Lister]

Hello JJJ, and welcome to SGL.

I, too, am a glasses wearer, and I think your 6.3mm Plossl will not have enough eye relief to use with glasses. My advice would be to wait until you have tried out the eyepieces you already have, and the Es82 and x2 Barlow, when they arrive, and then decide if there is an obvious gap in the magnifications available to you.

I have  several 1.25", 32mm Plossl eyepieces, and these tend to be my initial starting point for viewing an object.

I bought a 2", 56mm Plossl eyepiece, to go with my 10" Dob. It is heavy, and I found I needed a short extension tube to achieve focus. I use it on rare occasions, but there are few objects, or groups of objects, that need that wide angle view.

Geoff

[wongataa]

I would forget about filters for now.  If in the future you do consider them then how dark the skies are will affect what to look for.

As this is a new telescope the first thing to do is just use the eyepieces it comes with.  Get a feel for how well the work for you and what the celestial objects look like through them.  Once you have tried them all out then decide whether any new eyepieces may be worth buying.  Then you can decide whether you need different focal length eyepieces than what you have and whether the ones you have work with your glasses etc.

[Louis D]

Once the exit pupil gets small enough, weak astigmatism in your observing eye may become unobtrusive without correction.  Here's Tele Vue's chart for their Dioptrx line:

You can calculate the exit pupil by simply dividing the eyepiece focal length by the scope's f-ratio.  For instance, your 6.3mm Plossl in your f/5.9 scope yields a 6.3mm/5.9=1.1mm exit pupil.  According to the chart, you might to want use astigmatism correction if your cylinder prescription is 2.0 diopters or more.  I have 2.0 diopters of cylinder correction and can verify I can see sharpness improvement at a 1mm exit pupil when wearing eyeglasses.

For a low power eyepiece, I would probably recommend the 30mm APM UFF or its other brandings ( Meade UHD, Celestron Ultima Edge, Altair Ultra Flat Field, Tecnosky Ultra Flat, and Orion (US) Ultra Flat).  It is perfectly corrected edge to edge at f/6 and has plenty of eye relief for eyeglass wearers.  With a 5.1mm exit pupil in your scope, you would need well less than 0.5 diopter of cylinder correction to avoid wearing eyeglasses, so this eyepiece is a good choice if you have more than that amount of correction.  There are plenty of lower cost eyepieces with decent eye relief and wide field at or near this focal length, but they don't perform nearly as well at f/6 as this eyepiece.

For high power, if your astigmatism is low (1.0 diopter or less), you could get away with not wearing eyeglasses and use eyepieces with less eye relief.  Personally, I use a mix of Pentax XL and XW eyepieces with long eye relief at high powers because it's more comfortable, relaxing, and I almost never need to clean the eye lens of these eyepieces because my eyeglasses form a barrier to prevent eyelash gunk from getting on them.  The Morpheus line might also be a good choice at a somewhat lower price point.

Edited February 7, 2022 by Louis D

[Guest]

Look at the variable power 1.25 inch eyepieces.  They generally go from 8mm to 24mm.  They do very well with the planetary stuff.  I use an Orion 8 to 24 and I have used it to look at M31, the Orion Nebula, the Hercules Cluster and even the Ring Nebula.  It does reasonably well with these.  For my 2 inch stuff I run the Orion Q70s, all three will be right about 300 bucks.  They give solid performance.  

[Spile]

I have an 8” Dobsonian and have written up a number of tips and suggestions on my blog that may be of use to you. The link is below.