Louis D

7 minutes ago, Ken82 said:

F5 bresser. I did notice quite a bit of coma using my Celestron luminous 31, 23 and baader zoom. I’m not sure if that’s down to collimation or quality of the eyepiece ? 

Focus on a star at the edge of the eyepiece and rack focus on either side of that best focus.  If the star distorts into a tangential line on one side of best focus and a radial line on the other, that's astigmatism rather than coma you're predominately dealing with.  If it looks basically the same on either side like a teardrop fanning out away from the center, that's probably coma.  If the star splits into a rainbow radially, that's chromatic aberration.

Here's some daytime images comparing various fringe killer filters:

Most folks find the Baader Contrast Booster the most aggressive.

And this one shows how much of the spectrum different filters suppress:

The Contrast Booster works so well because it effectively cuts all violet and a bit of green-yellow-orange in the middle to reduce color shift.

If you want to do it justice, then you'll just have to get the TV Paracorr T2.😉  If you want to go cheaper on it, then there's the Explore Scientific CC or the GSO/Revelation CC.  I have the latter, and it just needs a 25mm extension tube to clean up 95% of the coma at f/5 to f/6.  It does need to be removed for high power work because it contributes a bit of spherical aberration that the TVPT2 doesn't.

4 hours ago, Shepdog said:

I'm keeping an eye on FB marketplace ...not sure of other places within my local area to look..id drive a few hours for a deal for sure..are the dobs difficult to use as long as they are collaminated? And how difficult is it to collaminate? I dont wanns get into something beyond my skill level....yet lol

Dobs are dirt simple to operate.  Just point and look.  Then nudge-nudge-nudge to keep the object in view.  The harder part is learning where objects are on the sky, and what to look for through the eyepiece to know you're on an object.

Collimation is a learned skill that takes a few tries to work through and become proficient at, but it's not difficult to do.  Once done, most Dobs hold their collimation pretty well and might just need a slight tweak to it over time.

14 hours ago, Shepdog said:

Bet the views are great out west

We certainly have lots of clear, stable nights.  However, I'm near enough to the Gulf that the high heat and humidity all night long during the summer can make observing miserable.  Winters are nice compared to up north.  No jet stream or subfreezing temperatures to deal with.

5 hours ago, jonathan said:

If you want to go big, then start big and stay there, but don't buy 8" and then think that 12" is going to be massively better because in my experience it just isn't, plus a 12" Dob is like the size of a man and awkward to handle for one person.

That's why I say to double your aperture to see a massive improvement.  I went from 3" to 8" to 15", and the improvement at each step was very noticeable.  I just can't fathom a 30" at this point. 😆

2 hours ago, Shepdog said:

Are you in the U.S Lois?

Thank you btw 

Yep, Texas.  Yee-haw, y'all. 🤠

I have a 3x that I bought first and have almost never used since buying a 2x.  It's just too much power for most conditions.  Power isn't so much the name of the game, it's aperture.  If you want to increase power while maintaining the quality of the view, you also have to increase the aperture of your scope.  That's why large Dobs are so popular.

2 hours ago, horseheadnebula said:

Hmm, you would think I would lose only 6 degrees with eyeglasses with Morpheus 6.5 mm? Then this could be good choise. Is magnification too close to my 8 mm Delos? 150 x versus 185 x?

Based on my Meade HD-60 6.5mm (which is a little tight on eye relief), I'd say only 10% of the field at most would be a bit difficult to see.  And yes, they'd be quite close in magnification.  5mm would be a much better step if you could find an older 5.2mm XL or an XW.

2 hours ago, horseheadnebula said:

Do you happen to know field stop diameter so I could calculate true field of view?

I've measured the 22mm AF70/Redline/Omegon/Ultima LX/etc. field stop to be 28.4mm, or just slightly larger than that possible in a 1.25" barrel.  It weighs 16.8 ounces and has exactly a 70 degree AFOV.  However, due to slight distortion, it has a 74 degree effective AFOV.  I'm guessing this is because magnification decreases slightly near the field stop, allowing more field to be squeezed in.

1 hour ago, horseheadnebula said:

Does this means that I would see shadow of secondary mirror (or some other problem)?

In my experience, secondary shadow is only an issue during daytime (solar) observations because your eye's pupil is so constricted that it approaches the size of the secondary shadow.  For instance, if you are using an eyepiece that provides a 6mm exit pupil, and you have a 35% by diameter secondary obstruction, the secondary shadow is 0.35*6mm=2.2mm.  Guess what, your eye's pupil constricts down to around 2mm during the daytime.  As a result, all you see in the center of the field is the shadow.  You literally have to move your eye off center and try to look "around" the secondary shadow to see anything at all.

The two problems with large exit pupils are that they lead to bright background skies and potential loss of usable aperture if your iris doesn't dilate enough to take in the entire exit pupil.  On the other hand, they're often the cheapest way to get the maximum field of view possible when choosing a "finder" eyepiece to help with centering objects in higher power eyepieces.

1 hour ago, horseheadnebula said:

Do you mean that eye cup should be screwed off from 22 mm Omegan Redline to have enough eye relief for glasses? I think I would hesitate to do that because I would be scare to get scratches on my eye glasses.

The eye cup is super rigid and won't fold down.   Since it's a 43mm thread, you could substitute a Morpheus eye cup if you're worried about scratching your eyeglasses.  I've done it myself just to prove it works fine.

I use many eyepieces without eye guards of any sort and haven't scratched my glasses yet.  If there's enough eye relief, you just hover above the eyepiece never touching it.  The one time I scratched an eyeglass lens was years ago with a 27mm Panoptic .  It had too little eye relief, yet I was determined to see the entire field of view, so I jammed my eyeglass lens into the top of the eyepiece, scratching it on the exposed eye lens retaining ring.  I was furious Tele Vue designed it that way.  It claims to have 19mm of eye relief when in reality it has only 14mm of usable eye relief with a sharp metal edge around the eye lens.

2 hours ago, Shepdog said:

I wish there was a different emoji than the heart..lol I appreciate that advice..

Yeah, apparently there's a lot of love of astronomy circulating around the UK.  😄

Apparently, it's a Mak in the UK and an achromat in the US.  However, I did find that Harrison Telescopes sells the achromat version:

https://www.harrisontelescopes.co.uk/acatalog/celestron-nexstar-102-slt-telescope.html

3 minutes ago, gilesco said:

Yes, you guys tend to get better prices than us in the UK, for tech goods we've called this the pound/dollar parity. We pay the same pounds as you pay dollars, and we keep our consumer rights that you don't have. We will have to rename it, as the pound is so weak now that we will have to change from parity to... a little more...

It's like everything in Europe relative to the US.  To cover all the costs associated with highly restrictive business laws, goods tend to be more expensive in Europe than in the US.  VAT alone adds costs just because every single business in the goods chain has to maintain meticulous tax records should they be audited.  This requires additional personnel to maintain those records.  In the US, sales tax is only collected when the item is sold to the end consumer.  Wholesalers are tax exempt and don't have to maintain any tax records because they never collect any taxes.  That's why most wholesalers in the US post "for sale only to the trade", otherwise they'd have to collect taxes on some sales.

24 minutes ago, Shepdog said:

I think I will go used like you advised...checking marketplace on FB now lol

I just know if i dont get the 8 i will end up buying it later lol

Be willing to meet someone halfway distance-wise.  Nashville, Knoxville, Lexington, and Louisville would all be larger markets than your home town yet make for reasonable drives.  You don't want to ship a Dob within the US.  They're just too big and heavy unless you have a merchant account.  Be patient, but always make it clear you want to buy it, or they'll move on to a more likely buyer.  You can always back out later if there are real issues when you see it in person.

6 hours ago, hardworkinpd said:

Ok, I'm back.........Looked at Mars last night. What's that black vertical line on it? I haven't seen it mentioned in searches, but I haven't searched it for that long either. Yeah I could make out some craters with my $80 scope. Also could make out a ring around Saturn but it was like looking at a pinhead (my eyes hurt today).

You might have been looking at Syrtis Major Planum.  Did it look sort of like the following images?

Along with the polar caps, it tends to be the highest contrast feature visible on Mars from the Earth.

40 minutes ago, randomic said:

In theory, the store loses exactly nothing, especially if the customer has to pay all the delivery costs associated.

Many stores in the US charge a 15% restocking fee because, by law in many parts of the US, you can't resell a used item as new.  You could try to charge the new price for it, but most folks will demand a discount once the fact it was a return/refurb is disclosed, which the 15% restocking fee covers.  Many unscrupulous retailers simply re-shrink-wrap the box and hope you don't complain.  In the US, return policies must be posted by retailers in most states.  If the retailer has a no-returns policy, that is perfectly legal.  The only exceptions under federal law are for 1. if the sold good is defective or 2. if the seller breaks the sales contract.

However, word of mouth gets around pretty quickly online about retailers with bad return policies, so most honor some sort of 30 day return policy.  However, you may be responsible for return shipping unless the item is defective or not as described.

44 minutes ago, Shepdog said:

Ok...well..i just started and trying to learn as much as i can..and picking out a christmas gift in advance lol thanks Louis...amd Faulksy

Pick out something quick and get on the waiting list at a reputable dealer or two if you want it by Christmas.  You might get lucky and find a good used scope while waiting.

6 minutes ago, Shayner2005 said:

I want to say that the focuser was in the middle, but I could be mistaken. I tried the straight-though mode, but it didn't seem to be any better. I did not try putting the barlow before the diagonal.

If the focuser was in the middle of its travel range when the image was the most compact, you may have issues other than limited in or out focus.

Can you point your scope at a distant tower during the daytime to test out the various combinations?  Ideally, it should be at least a couple of miles away to better simulate infinity focus as at night.

2 hours ago, Prism said:

I'll just repeat what I said to them - that it's surprising in a world where one can test out a car for a week or even try out underwear for size and then return it

At least in the US, most states don't allow you to return a car you bought.  A very few have lemon laws to allow for the return of seriously flawed vehicles.  Also, underwear cannot be returned once removed from its sealed packaging.

2 hours ago, Shepdog said:

If read every best under $300 article i can find and tried to find an answer here...can i get a good 8 inch dob in that price range? Or would I be regretting not waiting til i can spend $400?

This purchase will be what I hope to use for mid level user..

You'll find just about every retailer is out of stock on just about all telescopes, so you might as well continue saving up for a new 8" when they become available again.  That, and watch the astro classifieds (Cloudy Nights and Astromart) as well as Craigslist and Facebook Marketplace for used ones.

2 hours ago, faulksy said:

for your lower price bracket you could buy this from our sponsor https://www.firstlightoptics.com/dobsonians/skywatcher-skyliner-150p-dobsonian.html

Two problems:

1. Over $200 to ship to the US from FLO.
2. Out of stock for at least 40 days.

The 102slt is an f/6, so it should be fine with the 25mm + x3 Barlow = ~8mm.  It could be that the focuser doesn't have enough in-travel for that Barlow.  Do you have the focuser tube retracted all the way when the object image is smallest?  You could try removing the diagonal and using the scope in straight-through mode to see if it will come to focus.  You could also try putting the Barlow ahead of the diagonal to see if that combination comes to focus.  It will yield more than 3x in that configuration.

4 hours ago, badhex said:

Soooooo... sorry for the old thread bump

Nothing to be sorry for at all.  You started the thread.  It's almost expected that you report on your final decision/outcome no matter how much later.

Keep looking up.  I got some really good Mars views last night around 1:30am with my 8" Newt and binoviewers.  The latter made details pop into view that were only hinted at before at the same power in monovision.

53 minutes ago, John said:

Interesting comparing these prices:

https://www.firstlightoptics.com/bst-starguider-eyepieces/bst-starguider-60-12mm-ed-eyepiece.html

and

https://www.teleskop-express.de/shop/product_info.php/language/en/info/p4931_TS-Optics-1-25--ED-Okular-12mm---60--ebenes-Bildfeld---hoher-Kontrast.html

Exactly the same or subtle differences ?

£47 vs £85

 

 

I can cross import FLO's Starguiders, especially if I buy them 7 at a time, far cheaper than buying them new here from any US retailer.