The 10" Dobsonian Equatorial Telescope

[chrislee]

Ok guys, I made up my mind. I'm going to buy that used 8i. It's got all I want, good price point for me (only $400 more total than the SkyView Pro 120mm EQ Refractor), plus, it's only 8 mos old in perfect shape. It'll be perfect for the deep space objects, and it'll be pretty good at planetary observing (as I can adjustable magnifications with eyepieces. See below??) And lastly, astrophoto isn't in my immed. plans so Im not too worried about its arm mount right now, but am glad to see that reducer lens..pretty cool.<br /><br />A couple of last suggestions??<br /><br />TFW said: If you are getting an 8" SCT you are going to love a 32mm TeleVue Possl and a 20mm TeleVue Possl. Add a 2.5x TeleVue Powermate and you will have enough eyepieces to last awhile. Most 8" SCT's come with a 26mm or 28mm so you'll have <br /><br />32mm = 63x w/barlow 126x w/2.5 158x <br />28mm = 75x w/barlow 150x w/2.5 188x <br />20mm = 100x w/barlow 200x w/2.5 250x and you are maxed out her<br /><br />I don't quite understand why do that using barlows? Why not just pick a ep, like a 10mm to get to 200X? Isn't that simpler and have better optics? I must be missing something??<br /><br />Also, for collimating, it comes with those 'Bob's Knobs"...do I need a laser one then? I don't think so but thought I'd ask.<br /><br />Thanks alot for all the help and suggestions. I have learned alot and appreciated everything! I hope/think this is the right decision. <br /><br />Chris

 

[chrislee]

The guy just bailed, pulled the ad off astromart. Life's so wierd sometimes is all I can say. <br /><br />

 

[tfwthom]

Spent the day working on the clubs website so have not been around. (reworking the 2005 events page) www.siriuslookers.org <br /><br />You never know with Astromart...I've only bought once off there I go new most the time..or buy from another club member.<br /><br />Barlows save you money on eyepieces is all. If you have a 20mm why buy a 10mm, use a barlow. You double your eyepiece collection without the expence. Always buy a top quality barlow. <div class="Discussion_UserSignature"> <font size="1" color="#3366ff">www.siriuslookers.org</font> </div>

 

[bbrock]

Chris<br /><br />Lazer Collimators make the process of collimitating fast, easy and very accurate. I checked my collimation last night and it took 2 minutes. Did it in the dark. <br /><br />Polar Alignment is necessary for Equatorial Mounts to track. The idea is to align the Right Ascention (RA) Axis of the scope with the North Celestial Pole ( if you are North of the Celestial Equator ). Then if you point to an object and a motor turns the scope at the sideral rate ( = 15 arcseconds / second ) about the RA Axis, then the scope will always point at the object. <br /><br />For most casual observation, it isn't critical that your polar alignment is accurate. If you plan on using photography, it is critical. If you are using very high magnification, it helps to spend the time to accurately polar align. <br /><br />Most equatorial mounts come with a polar alignment scope. Some are illuminated which helps perform this exercise in the dark. The PAScope greatly increases accuracy. However, check the PAScope when you first get it. Often the PAScope needs alignment itself which is the cause of much frustration in the amature astronomy ranks. Most folks assume it comes from the factory axis aligned. I bet none of them do. Mine was off by 0.5 arc-degree. <br /><br />Bill

 

[chrislee]

Well, woke up this am to an email saying the seller felt bad and would sell it to me afterall. Ok then <img src="/images/icons/smile.gif" />)<br /><br />Bill, can I get away using just these Bobs knobs to Collimate or do I need a lazer like this: Kendrick SCT Laser Collimator (read a good review of this one)<br /><br />Oh and Thanks for that exc. explanation!!<br /><br />And TFW, you sugg: 32mm TeleVue Possl and a 20mm TeleVue Possl. Add a 2.5x TeleVue Powermate ...these prices is 1/2 as much as those naglers. So they must be at least pretty decent I'd guess? And do you all buy the 1.25" ones too since that's the sizes that comes with the scope??<br /><br />And also, Which barstow?? There's alot of brands..is the Orion SHorty good at $80?... or should I spend a bit more on the Televue 2x Barlow 1.25" for $105??<br /><br />Crazyeddy, yes I plan on wearing my glasses, So the barlow keeping good eye relief is important. Thx for explaining that to me.<br /><br />Thanks for the suggestions! It's making this last task of buying needed accessories much easier!<br /><br />Chris

 

[bbrock]

Chris<br /><br />I can't give you an honist answer about the Bobs Knobs vs Kendrick SCT Laser Collimator. Perhaps someone else can answer that. I've used both lazer and peep hole on my reflector and I would have a very difficult time with the peep hole through focuser in the dark. Secondly, I don't think I could get the precise collimation using eye sight guestimation lookng through the peep. <br /><br />Then again, I have never collimated an SCT. I don't think they are as prone to mis-align as reflector primary mirrors are. However, its nice to check and know that your optics are in alignment. <br /><br />I own an Orion Shorty 2x barlow and it is very clear and sharp. This barlow is excellent at $80. I'm sure the Televue is excellent also. <br /><br />In all of the discussions under this thread, nobody has mentioned Exit Pupil. (( Yes, there is a topic we haven't covered. )) Perhaps we will wait till some other time. <br /><br />Bill

 

[tfwthom]

You are entering the big debate about changing the 1.25" diagonal to a 2" diagonal. (and the visual back)<br /><br />My opinion is that unless you already have 2" eyepieces it's not worth the trouble. The baffle tube on the 8" and 10" SCTs is only 1.5" anyway so you can't get the full use out of the 2" eyepiece. The 11"+ SCTs (mostly) come with a 2" diagonal and a larger baffle tube so that's not a problem. <br /><br />On barlows....well I have a Meade 2x that I use in the LX90 only, it shows "color" in the TV85 and the FS128. I have the 2.5x and 5x Powermates that I use in the TV85 and the FS128. (BTW a nice combo in the FS128 is a 15mm Possl and either Powermate)<br /><br />I swear by TeleVue eyepieces (when a new eyepiece line comes out the question asked is "how does it compare to a TeleVue?" so why buy anything else) Also test drive the eyepieces in your scope, I thought I wanted a 40mm till I tried one out in the LX90, it was like looking down a cardboard tube. Al has a page on his website about SCT eyepieces http://televue.com/engine/page.asp?ID=222<br /><br />My current eyepiece collection across the 3 scopes:<br /><br />(2) 32mm TeleVue possl 1.25"<br />(1) 26mm Meade possl 1.25"<br />(2) 20mm TeleVue possl 1.25"<br />(1) 15mm Meade possl 1.25"<br />(1) 13mm TeleVue Nagler type1 1.25" and 2"<br />(1) 8 - 24mm TeleVue zoom 1.25"<br />(1) 3 - 6mm TeleVue Nagler zoom 1.25"<br /><br />I mix and match across the scopes to get the best views.<br /><br /><br />One of our club has an SCT website for beginners that you might find useful http://sctscopes.net/index.html<br /><br />I hardly ever have to collimate my SCT maybe once or twice a year. The way I transport the scope it doesn't get bounced much so doesn't get knocked out of alignment. Using a laser is a pain (a whole lot of things have to be done to do it right, things like the target has to be square to <div class="Discussion_UserSignature"> <font size="1" color="#3366ff">www.siriuslookers.org</font> </div>

 

[chrislee]

First off...Thanks for ALL that information and great links! Those will help alot! Seems those Bobs Knobs will work fine after reading that article. <br /><br />LOL...information overload...too late guys hehehe<br />Yeah, I dont understand the exit pupil thing, I guess that's another thing to learn about...but just you guys telling me what works with what is good enough for me right now lol <br /><br />*(OH, btw, can I also use these ep's that are designed for glasses if I'm wearing my contacts instead that particular night?..kinda important I guess)<br /><br /><You are entering the big debate about changing the 1.25" diagonal to a 2" diagonal. /><br /><br />I didn't even know there was one lol The 1.25" is fine with. Didn't know about the11"s using the 2". <br /><br /><Get involved in a local astronomy club, you can get more help from them then anyplace else. Besides you can test drive their equipment to see if you like it. (that's where I tried out a helographic (sp) laser and found I didn't want to go through the trouble.) Observing in a groupe is more fun and safer (after all you heading out to the boonies what happens if your car doesn't start and most of the places are so far out that cell phones don't work) /><br /><br />Im sure we certainly will TFW! I think it sounds like alot of fun. Theres actually a local gathering to watch the sun by a local bunch this coming week, but I can't bring my partner cause that'll ruin the xmas surprise lol...but maybe I can 'sneak' away and go myself ...terrible I know! lol<br /><br />I really appreciate again those links!! I'll learn alot from them I'm sure!<br /><br />And one thing guys, I plan on following the advice to get the following: Televue 32mm, 20mm and the 2x barlow (i can get that 2.5x later).....but I'm wondering if I should get it NOW, or can I enjoy the scope enough using just the stock 25mm Plossl for now? I'll only have 80x though. I can get those three for another $300.<br />Just wondering if I should

 

[tfwthom]

My opinion....get the 32mm and the 20mm eyepieces. Hold off on anything else till you get a chance to test drive the other toys. Maybe you will find they aren't worth it to you.<br /><br />When I do public outreach the only eyepieces I use are the 32mm and the 20mm in the LX90. <br /><br />I wear glasses...at least I did till the 1st of this year when I switched to contacts again (I had hard contacts back in the 70s and they were such a pain) (I'm old lol)<br />The eyepieces work just fine either way. <div class="Discussion_UserSignature"> <font size="1" color="#3366ff">www.siriuslookers.org</font> </div>

 

[chrislee]

Thanks TFW, sounds good. Good to hear about the contacts issue.

 

[chrislee]

Hi guys again <img src="/images/icons/smile.gif" /> <br /><br />I finished this purchase today! I bought the Plossl's 32mm, 20mm, and the TeleVue 2.5x Powermate (had to buy the T ring adaptor too). <br /><br />That'll give me the magnifications of:<br /> 63x, 80x, 100x, 158x, 200x, and 250x.<br /><br />That's 2 lows, 2 mediums, and 2 highs. And that's why I chose it over the 2X Barlow even though it was a bit more spendy. <br /><br />I also got the Orion small eyepiece case to keep them scratch free. <br /><br />Here's a bit of a splurge: I got the TeleVue 1.25" Everbrite Star Diagonal after reading that SCT users webpage. They said it made a big difference over the stock diagonal. <br /><br />So total cost incl the 8i just about $1700. Not too far off from my budget, and I got a scope that we can setup with ease and use the GOTO to learn astronomy more efficiently for us, and lastly, it stores easily. Plus, I got some great accessories....Thanks for the suggestions!<br /><br />Anyway, I just wanted to let you all know how it ended <img src="/images/icons/smile.gif" /><br /><br />Great forum! A bit above my head from some of the other topics hehe And I also wanted to apologize for jumping in on this thread and talking about something other than the 10" Dob. I know it's not the best etiquette and again, sorry!<br /><br /><br />But lastly, before I leave you guys alone <img src="/images/icons/smile.gif" /> <br /><br />A BIG THUMBS UP TO Bill, Crazyeddy, and TFWTom for the all the help! I know I asked ALOT of questions and I just wanted to say "Thanks" !!<br /><br />Take Care and an early Merry Christmas to all!<br /><br />Chris<br />

 

[tfwthom]

OK Chris.....now when you going to make the Grand Canyon Star Party? I want to see this setup.<br /><br />The National Park Service sponsors the event, the Tucson club (TAAA http://www.tucsonastronomy.org/ ) organizes it ever June on the South Rim. <br /><br />Picture about 50+ amateur astronomers (and some pros) setting up scopes for the 100s of people visiting the canyon. The public leaves about 11:00pm and the rest of the 8 nights is spent under some of the darkest skies in the counrty. What you would learn about astronomy in the week there would take years to learn anywhere else.<br /><br />We have had people from all over the country join us, like Elaine, she drives from around Roanoke Virginia, or Geoff from Chicago. We have even had one or two fly in (last year one flew in from France another from FL) <br /><br />The 2005 dates are not set yet but we are talking about June 4th to 12th. Check the TAAA website after the 1st of the year. http://www.tucsonastronomy.org/gcsp.html <div class="Discussion_UserSignature"> <font size="1" color="#3366ff">www.siriuslookers.org</font> </div>

 

[chrislee]

Now that DOES look like a cool event! Something to consider for a fun and educating little vacation <img src="/images/icons/smile.gif" /><br /><br />I'll keep an eye out for the details. Thanks.<br /><br /><br />Guys, should I have instead of upgrading to the Televue star diagonal first, should I have replaced the Celstron's Star Pointer non-magnifying variable brightness red dot-type finderscope for the Telrad illuminated non-magnifying Telrad finder? Price diff. was negligable.<br /><br />Chris