Advice

[Acumeon]

I am a noob to astronomy. 

For the last few weeks I have been reading up on my new hobby, wife not happy about another hobby (lol). Although, after showing off Jupiter and Orion I may have a new awesome stargazing partner!  Anyway, I have an Omni XLT 150 Newtonian. This being my first scope there was no reference as to what is good and bad. Read a few reviews on before I purchased it off of craigslist.

Scope needed some TLC. Cleaned the primary and secondary mirrors (after reading and watching several tutorials), cleaned out the tube, tightened the spider screws on the tube and secondary mirror (screw holding secondary was almost unscrewed probably from being calibrated and never checked how far unscrewed it was). The eyepieces that came with the scope were okay. An omni 32, vixen 20, vixen 13, celestron 8 - 24 zoom and an omni 2x barlow. The eyepieces are all between 40 - 60 degree AFOV. A laser collimator also came with the scope.

Having used the scope a few times I've notice a few things. The eyepieces needed to go. Well, at the time it was my belief the poor images were due to the quality of the eyepieces. So, I bought the 31mm and 10mm Celestron Luminous eyepieces with the 2.5x Luminous Barlow. Was looking at Explore Scientific's 82 degree AFOV line but went with Celestron due to price. What an amazing difference! Will be picking up the rest of the luminous line when I can.  After being blinded by the Moon, you read about it but us rebels don't believe that it could be that bad, I bought a Lumicon #80A and ND13. Again, wow, what a difference. Also picked up a Celestron LPR filter. Not sure about that one yet. Seems to turn every thing blue. Not sure if it really creates a darker background.

So, now that I have better eyepieces other things are needing addressed. There is a lot of reflections. The primary and focus tubes are painted with a satin black. There is a great deal of diffraction from the 4 vane spider and possibly the focus tube as this is a 6 inch mirror and the primary tube is only 7 inches causing the focus tube to be in the path of light to the primary mirror.

My questions are:

1. Would flocking the tube help with reflections enough that it is worth doing?

2. Would replacing the vanes with curved vanes help control diffraction or should I just use filters?

3. Would cutting down the focus tube by about an inch harm anything?

4. Is there anything else I should or could change, within reason, with my setup to either help or enhance the experience?  FYI, I am currently working on building a DIY drive system and autoguider.

Thanks for you time.

[ronin]

1. Would flocking the tube help with reflections enough that it is worth doing?

2. Would replacing the vanes with curved vanes help control diffraction or should I just use filters?

3. Would cutting down the focus tube by about an inch harm anything?

4. Is there anything else I should or could change, within reason, with my setup to either help or enhance the experience?  FYI, I am currently working on building a DIY drive system and autoguider.

1: Should help as there is generally more reflection at shallow angles then people realise. Just look at a road in reasonable sunlight.

2: Curved vanes will "help" in that they remove the distinct spikes, but the diffraction remains in one form or another, the general image will have a more overall loss of contrast. Cannot think of a filter that would do anything useful in this respect. Diffraction spikes are a consequence of a newtonian, they cannot be filtered out. Look at Hubble images, they have diffraction spikes.

3: Quite possibly and I cannot see what it will accomplish. I can easily see you cutting an inch off then having to buy a 1" entender.

4: Just check out the collimation and other small aspects. There are limitations of what a 150 Newtonian can do, equally there limits on all scopes.

[Acumeon]

Thank you for taking the time to respond.

Curved vanes will "help" in that they remove the distinct spikes, but the diffraction remains in one form or another, the general image will have a more overall loss of contrast. Cannot think of a filter that would do anything useful in this respect. Diffraction spikes are a consequence of a newtonian, they cannot be filtered out.

The goal was not to eliminate the spikes, as I read it is not possible, just make them less noticeable.

There are limitations of what a 1There are limitations of what a 150 Newtonian can do50 Newtonian can do

 Yes, I know there are limits, but at the time this is what I have access to.

I guess what the real question is rather are the items listed in my questions worth doing on this scope, or should the time and money be saved. Will there be a big difference in the before and after?

[Dave In Vermont]

With you having tightened the secondary and all, I'd start by doing a full collimation to your scope. Here's one of the best How To guides:

http://www.astro-baby.com/collimation/astro%20babys%20collimation%20guide.htm

I hope this helps.

Clear Skies,

Dave

[SpaceWalker]

1. Would flocking the tube help with reflections enough that it is worth doing?

Yes it'll help. I'd also recommend you to make a due shield/tube extension (hood) like shown here or here. I made an extention tube for my Dob from a tourist mat. Contrast improvement was obvious even without flocking. But the flocking will add to it as well. You can flock only the area against focuser and the secondary mirror holder like suggested in #5 here so you won't have to disassemble the OTA completely. Flocking area against focuser plus tube extension/hood will work fine together.

 

4. Is there anything else I should or could change, within reason, with my setup to either help or enhance the experience?  FYI, I am currently working on building a DIY drive system and autoguider.

Check out this thread, there are posted a lot of mods some of which you may find useful.

Also wanted to warn you about the Luminos. They are inexpensive on purpose and have some serious problems (e.g. EoFB, etc) so I'd better save for longer and buy ES82, Maxvision, ES68 etc. You may want to look into next threads on CN discussing the Luminos problems.

Celestron 82° Luminos eyeieces

Luminos have arrived

EOFB in Luminos - it's there, but it's incredibly minor

[Lowjiber]

I have one of those Newts.  Frankly, every f/5 6" Newt I've ever owned is very touchy to a great collimation, and you sorta (respectfully) danced around that in your original post.  Those short-tubed 6" Newts have never really been all that popular from a visual perspective, as they lean more toward photography and aren't the best at that either.    I use mine on occasion to take some decent exposures with a DSLR.

Being new to the hobby, I'd suggest (again, respectfully) that you get the collimation down perfectly before wasting any time and effort aimed at flocking; throwing eyepieces at a scope that may need collmation; or chopping an inch off of the focuser tube.  (I still don't understand that last one.)

That scope, like many fast Newts, suffers from coma.  However, I've never noticed an insurrmountable diffraction spike problem with mine, they are a fact-of-life with these scopes.  I don't see your logic to using filters to control diffraction.

Since you're new to the hobby, try to find an astronomy club close to you.  It's likely they'll have a member who can give you help with the collimation, which appears to be the major problem.

Clear, Dark Skies

[rwilkey]

Hi Acumeon, the Luminos (like their forebears, the Axiom LX) do suffer a bit from internal reflection, wheras the ES82's do not