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Any missing accessories for 18" dob?

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#1 Kevdog

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Posted 22 April 2014 - 04:42 PM

I have an 18" Obsession and I think I've run out of things to buy!

I have:
ES82 30mm, 18mm, 11mm, 6.7mm
2x barlow

Laser Collimator (good quality) with holigraphic crosshairs (for secondary alignment)
Barlow for laser and target

Telrad
10x50 RACI

Fan for mirror, plus battery pack.

Red light
Pocket Sky Atlas
Sky Safari (for android)


Is there anything I'm missing that would be handy? I really enjoy the scope now and have my workflow for setup and teardown pretty quick, especially since I'm at home and just wheel it in and out of the garage.

Thanks for any thoughts.

#2 David Knisely

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Posted 22 April 2014 - 05:11 PM

Get a good set of nebula filters. I recommend getting both the DGM Optics NPB narrow-band filter as well as the Lumicon OIII filter. Together, they just about cover all the bases as far as enhancing emission and planetary nebulae. Also, if you are really going after faint stuff, I would recommend Sky Safari PRO rather than just Sky Safari. Otherwise, an 18 inch would be better off with a more detailed book atlas like the 3-volume Uranometria 2000.0 (2nd edition). Clear skies to you.

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#3 bluesteel

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Posted 22 April 2014 - 05:17 PM

What types of objects are you tending to view the most?

Observing chair? Dew heaters? Mosquito repellent? Table for your gear? Thermos for hot or cold beverages? Equatorial platform?

#4 klim

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Posted 22 April 2014 - 07:48 PM

Binoviewer?

#5 omahaastro

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Posted 22 April 2014 - 09:44 PM

Astrosystems truss bag and scope cover
https://www.astrosys...biz/Obspage.htm

#6 DarkSkysRFun

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Posted 22 April 2014 - 10:00 PM

Binoviewer?


+1

#7 Fred1

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Posted 22 April 2014 - 10:47 PM

Binoviewer?


+1


Yep! Can't live without 'em.

Also, a suitable vehicle that can accommodate a comfortable sleeping arrangement to haul it all to a very dark site for overnight observing sessions. :cool:

#8 star drop

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Posted 23 April 2014 - 09:13 AM

Get a Paracorr.

#9 Kevdog

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Posted 23 April 2014 - 09:57 AM

Thanks for the posts guys... going to answer all at once.

I forgot to mention I have the DGM NPB filter (2") and a set of color filters (1.25") plus a variable polarizing moon filter. I need to remember and use the NPB more. I'll have to think about a Lumicon OIII.

So far I'm not going for the faint stuff and there's still plenty of brighter stuff I haven't seen. Darn, just looked and I missed the half off intro price for Sky Safari 4! Was going to get the pro at $20!

As for viewing objects, I look at mainly galaxies, nebula, globs and planets.

With the 18" Obsession I'm standing most of the time and sometime on a ladder.
In AZ, no dew or mosquitos. I do have big slab bench outside that acts as my table.

Oh yes, binoviewer. I may have to look into that again. Was going to get one for my C11, then got sidetracked!

I'll still have to think about the Paracorr. At this point I don't notice the coma in my ES82 30mm, but maybe I would once it is gone. I know my scope is short on in-focus. Does the paracorr make that better or worse? Basically once I put the 1.25" eyepieces in an adapter, I barely have room to get focus.

Same question goes with the binoviewer? Do I need more in-focus? I think I do right? If so I'd have to shorten my truss poles and I don't know if I'm ready for that.

Putting these ideas on my list! Thanks!

#10 okieav8r

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Posted 23 April 2014 - 10:58 AM

Up until last fall, I was using a Denk super system bino in my 18" Obsession, and had no focusing issues at all. If I had to shorten the poles to get it to focus, I'd have forgone using a binoviewer altogether.

Also, I consider a Paracorr to be essential gear for my telescope.

#11 Kevdog

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Posted 24 April 2014 - 10:07 AM

Ironically, while trying to make a new target for my barlowed laser attachment, the switch on my laser collimator (a 17 year old astrotech that came with the 18 Obsession) has almost given up. I have to switch it 5 or 6 times to finally get it to "take" and stay on. Also I noticed that the laser beam has a large "chunk" out of it so the laser looked like a partially eclipsed moon!

So I ordered the glatter 2" laser and barlow attachment.

Will still think about a coma corrector.

#12 maakhand

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Posted 24 April 2014 - 10:56 AM

surprised that its not mentioned yet.
2" catseye autocollimator.

#13 GeneT

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Posted 24 April 2014 - 07:30 PM

Up until last fall, I was using a Denk super system bino in my 18" Obsession, and had no focusing issues at all. If I had to shorten the poles to get it to focus, I'd have forgone using a binoviewer altogether.


Several have posted that they had in-focus problems with a binoviewer. You had none with your Obsession? I have owned two Obsessions and had to trim about a half inch off the trusses to get focus.

Why would you be against trimming them, if necessary?

#14 okieav8r

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Posted 24 April 2014 - 07:59 PM

Up until last fall, I was using a Denk super system bino in my 18" Obsession, and had no focusing issues at all. If I had to shorten the poles to get it to focus, I'd have forgone using a binoviewer altogether.


Several have posted that they had in-focus problems with a binoviewer. You had none with your Obsession? I have owned two Obsessions and had to trim about a half inch off the trusses to get focus.

Why would you be against trimming them, if necessary?


Hi Gene. The Denk super system is designed to work with any telescope, regardless of what type it is. It probably has a lot to do with some of the accessories that come with it. You add or remove some spacers and specialty lenses, depending on what type of scope you use it with. It's the only bino I used in my telescope, so I can't comment as to whether other binos would have issues or not.

Oh, I reckon I wouldn't mind cutting the truss tubes on an Obsession too much, since they are nothing but electrical conduit that can be purchased cheaply at Lowes or Home Depot. In that regard, they are easily replaceable. But I sure wouldn't want to do it on a telescope that has a more specialized truss design. If I found that I just wasn't all that into binoviewing, which ended up being the case with me, I'd end up with a telescope that might have issues focusing with regular eyepieces because of the modification. Viewing with the binos was fun for awhile, but the novelty soon wore off for me. I sold my Denks last fall.

#15 bgi

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Posted 11 May 2014 - 04:28 AM

For sure ditto on the paracorr and 2" autocollimator, maybe a cheshire and sight tube.

You may want to consider one or two simpler high-power eye pieces for planets or planetary nebulae on the nights of good seeing. Head over to the eyepiece forum and you'll find plenty of healthy debate!

I didn't see mention of a drive system. If it doesn't have one, maybe install a goto-track system of your choosing. Being able to relax and keep an object centered contributes greatly to your ability to see detail - esp at high powers.

#16 kfiscus

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Posted 11 May 2014 - 01:23 PM

A sidekick? I would make myself available.

But seriously, a filter slide and 2" O-III, NPB, and H-beta filters.

#17 JimMo

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Posted 11 May 2014 - 01:46 PM

Get an Argo Navis this year and a Servocat next year. I installed it all myself and wonder how I ever got along star hopping. Five to ten objects a night turned into as many as I want, more time observing and less hunting down the object. This year's upgrade was a SkyFi and star safari 4 Pro for my IPad. I did get it on sale at 1/2 off. I have much more relaxed observing sessions since the Servocat provided tracking and I carry much less media with me since the SS/IPad upgrade. After seven years this telescope if finally finished.

#18 rnc39560

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Posted 11 May 2014 - 02:21 PM

I tire for a secondary cage! It would more closely resemble the scope the ingenious little boy gave you for father's day last year! Wait, it was father's day right?

#19 WattleHill

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Posted 11 May 2014 - 09:27 PM

Get an Argo Navis this year and a Servocat next year. I installed it all myself and wonder how I ever got along star hopping. Five to ten objects a night turned into as many as I want, more time observing and less hunting down the object. This year's upgrade was a SkyFi and star safari 4 Pro for my IPad. I did get it on sale at 1/2 off. I have much more relaxed observing sessions since the Servocat provided tracking and I carry much less media with me since the SS/IPad upgrade. After seven years this telescope if finally finished.


+1 for an Argo Navis. I have an 18-inch f4.5 Obsession and using it with an Argo Navis is a dream come true. I've been a star hopper all my astro life and resisted any form of technology to compliment my equipment (no particular reason, I just was happy without it). Then I fitted the Argo Navis. From flicking the power switch, it take no more than 90 seconds to do a simple alignment and I am ready to observe. What's more I can locate any object in it's database instantly and 99% accuracy. The 1% is from objects that appear just on the esge of field. Well worth the coin!

#20 alexvh

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Posted 12 May 2014 - 03:20 AM

David, what filters should be used on galaxies? Are filters worth it when viewing from dark skies?

#21 kfiscus

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Posted 12 May 2014 - 06:41 AM

I'm not David but I'll respond. Filters won't do much for galaxies but excel on planetary and gaseous nebulae. Filters like the O-III and NPB are useful under dark skies as well as light-polluted ones. They will give you completely new levels of detail in old favorites and make many objects observable that were barely detectable unfiltered.

#22 Starman1

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Posted 12 May 2014 - 11:02 AM

Short list of what I take to the field:

Base of Dob.
pole bag
upper section of dob
leather jacket
Digital Camera
Eyepiece box
Accessories case
cell phone battery charger
Folding table
Folding Deck Chair (2)
Starmaster Observer's chair
Thermos
food, water, other drinks (coffee)
battery charger and extension cord
Large bag with observing guides, star atlases, notebooks, logs.
Butane stove and coffee pot.
2 pillows
sleeping bag
sleeping pad
blanket
Telrad
scope cover
sunglasses/cap
binoculars
Battery for fans, DSC (2 for when one goes dead in the cold)
Milk Crate (to carry a lot of the stuff
A few counterweights of various weights for balancing
Large duffle bag with 15 pcs winter clothing
Heavy boots with wool sox
Assortment of gloves

My accessories case has in it:
--red LED flashlight
--leveling pads for feet of scope
--pens that write in sub freezing temps
--Paracorr
--DSC w/hardware
--power director
--cleaning stuff
--box with all necessary tools to work on scope
--box with miscellaneous screws and small parts for scope
--Catseye Collimation tools
--SQM to measure sky darkness
--green laser pointer
--IR thermometer to track mirror temp
--red LED clip-on light (for use in car)
--accurate level
--Ronchi testing eyepiece
--spare batteries for Telrad, SQM, IR thermometer, green laser, et.al.
--filter slide
--all my filters (about 20 or so, including 6 nebula filters)

Observing at home, you may not need all of those things with you. But you do have them handy in the house, eh? If not, you might still be able to use a few more acquisitions.

As for eyepieces, can one ever be done with buying them? I'm not certain of that. But if your scope is f/4.5, for sure you're missing a coma corrector.

#23 mantrain

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Posted 12 May 2014 - 10:56 PM

Totally ignorant question but what will the paracorr help with?

Also of all of you that have binoviewers, how often do you use them? I have considered that one myself.

And did I miss anyone recommending a ArgoNavis?

#24 Starman1

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Posted 13 May 2014 - 12:49 AM

Totally ignorant question but what will the paracorr help with?

Also of all of you that have binoviewers, how often do you use them? I have considered that one myself.

And did I miss anyone recommending a ArgoNavis?


Newtonian telescopes have paraboloidal mirrors. Paraboloidal mirrors faster than f/6 or so produce star images at the edge of the field that are spread out into little fan shapes instead of points. That fan looks a little like hair (coma is the Latin word for hair).
Coma is an aberration that grows linearly from the center of the field out.
The faster the scope, the faster coma grows in size and severity.
A coma corrector applies reverse coma from the center of the field out to cancel the coma in the field of view so star images at the edge of the field are just as tight and small as those in the center (though other aberrations in the eyepiece may make this impossible).
A Paracorr is a TeleVue brand coma corrector which inserts in the focuser and is used a lot like a barlow with a helical top.

Though coma, on paper, is visible in a wide field all the way to f/8, in practice no one notices until you get down to about f/5, and, at f/5 most don't use a coma corrector.
By f/4.5, most see the reason for one but some won't use one for a variety of reasons. Without one, though, only the center 25% of the field will be sharp at f/4.5.
By f/4, nearly everyone uses one because the star images become really smeared out from fairly close to the center of the field and getting worse as you go out.
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Binoviewers work great if neither of your eyes has any vision problems, and they seem to work best on bright targets. For faint stuff near the limit of the scope, you're probably better off without them.
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Argo Navis is currently the most complete of the DSC boxes, with the largest object list, the largest personal data entry memory, and the ability to compensate for inaccuracies in the scope's manufacture. It's also the most expensive. LED screen with adjustable brightness.
I'd rate the Sky Commander a close second, but with a smaller object memory (though still pretty large). It can be powered by 12V if a heater for the LCD screen is necessary. Of the DSCs, this is the one that needs supplemental dimming of the screen. Cost effective.
And the Tangent (JMI, Lumicon, Discovery, et.al) boxes are #3 in my book, but only because the number of button pushes to go from target to target is so large. Otherwise, they're just as accurate. LED screen with adjustable brightness. Long battery life.

#25 mantrain

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Posted 13 May 2014 - 01:21 AM

Do you have anything against the NGC MAX?

Well I am at F 4.5 so I suppose the paracorr is certainly on my short-list.

The bino-viewer for me can wait. I have mild astigmatism. And I tend to look at DSO's. But I enjoy swimming in the summer milky way. I imagine a bino-viewer would be great for that.






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