Louis D

5 hours ago, dweller25 said:

I am visual only and have found that doublet refractors work just fine.

Agreed on triplets.  I have a 90mm FPL-53 triplet, and it takes about 30 minutes to reach equilibrium, which is quite annoying for a grab and go scope.

@StarWomble Since neither triplet you're looking at has FPL-53/55 or FCD-100 glass, you might as well get a FPL-53/55 or FCD-100 doublet.  The CA will be about the same, but it will be lighter and quicker to equilibriate.  The Altair Wave Series 125 EDF, TS-Optics Doublet SD-APO 125mm, etc. have been well received and have an FPL-53 doublet in your price range.

It sure looks like a GSO made Dob.  These have been branded as Zhumell at first and later as Apertura, along with Orion's recent SkyLine, here in the US, Revelation in UK, and Delta Optical in Poland.  Anyone know of other brandings?

I'm always concerned about the altitude bearings based on the number of them up for sale on CN classifieds.  Either they mounted the tube with rings to a EQ mount or they mounted their own bearings (probably larger) and made a new Dob base to match.  I'd love to see GSO offer a JOC style Dob altitude bearing as on the ES and Bresser Dobs.

4 hours ago, pete_l said:

I use a barbecue cover and that seems to be quite successful.

I quit using these covers over my grill years ago.  They would always disintegrate within a year outside in the Texas sun.  It turns out grills don't really benefit from a cover anyway.

Try putting a heavy duty garbage bag over the rig and under the tough cover as additional leak insurance.

Shop for contractor clean-up bags or 55 gallon drum liners in the 3 to 7 mil thickness for extra security.  They're insanely tough, but probably not UV resistant, so the need for another cover.

The center one generally is for adjusting height along the optical axis and rotation of the holder along that same axis.  There's generally no reason to change either from the factory setting.

The three on the back of holder need to be loosened in a counter-clockwise manner before the holder can be tipped at all.  There's nothing spring loaded in there.  All three are snugged up tight against the holder.

Before mucking about with them, first check to see if the secondary is already centered and square to the focuser with a sight tube.  It should be circular and centered in the tube.

After that, verify that the secondary is pointing straight at the primary.  I generally use a laser collimator for this.  If the beam hits the center of the primary mirror center mark, you're done.

Last, check that the primary is aligned with the optical axis.  I generally use an Aline for this.  Once the secondary shadow is perfectly centered within the primary mirror center mark (easiest if it's a ring mark), you're done.

7 hours ago, Pixies said:

I'm not sold on wide-field views. I have an 18mm version of the often recommended Nirvana 82deg EPs , but just don't get on with it. It's like  sitting too close to the cinema screen!

Seriously, though, some of that may be due to lack of eye relief or having a difficult to hold exit pupil, either of which can make it tiresome to use for extended periods of time.

If you've got the bucks, try a 17mm ES-92 sometime instead.  It has 17mm of usable eye relief and an easy to hold exit pupil.  The view is just all there, all at once.  You don't have push in hard or tip your head to see the edges.  Just look straight ahead while hovering above the eyepiece, and it appears to be full of stars well out into your peripheral vision.

7 minutes ago, SMF said:

Hi, I agree the ‘really useful’ boxes are excellent and I’ve found nothing better for my purposes but a word of warning.

I use them for work storing spare parts in them in the back of the truck and have noticed that when cold they get really brittle.

In the depths of winter working at night/early morning quite a few have broken and as a result I dropped them.

The last thing you want is them to break as you carry your pride and joy in them. 

And boy are the edges sharp.

Steve

Not surprising since their website has the following spec right near the top of the page:

All items have a working temperature of -15°C to +80°C.

It regularly got down to -25°C where I grew up, so that would mean keeping this style storage box inside during the winter.

1 hour ago, Pixies said:

It's like  sitting too close to the cinema screen!

Do you also prefer standing well back from a window when looking outside? 😉😁

1 hour ago, Mr niall said:

In the end I bought a full set of “Series 500” plossls (all 9 of them) from China for £85.

I wonder if they're from the same line reviewed on CN in 2006.

That's a great price.  The best I could find for them was $186 on ebay.

4 hours ago, Giles_B said:

There might be a cheap solution that is a step up from duffell bags and bubble wrap

Are you dissing my travel solution? 😉😆

The original CN thread on eyepiece graphs.

Here's the original chart that started that thread which Tom then modified:

2 hours ago, Zermelo said:

So yes, you can use a 40mm, 50°, 1.25" eyepiece, which will give you a lower magnification than the 32mm but no advantage in field of view; and you will lose some of the light on the way (vignetting).

Explanation sounds correct except for this bit.  The amount of light integrated across the two fields of view (32mm and 40mm) should be the same since each has the same field stop (and likely field lens) size.  The 40mm simply compresses that light into a smaller apparent field of view yielding a larger exit pupil which can be useful with aggressive nebula filters such as an OIII filter.

14 hours ago, iPonchco said:

I want to get a 2" eyepiece, so that I can easily remove my dslr and pop in my EP without using any adapters.  To me it makes sense.

You can get low cost 2" to 1.25" adapters which you can leave permanently attached to your 1.25" eyepieces to avoid having to deal with an adapter on the fly.  You can even replace the thumbscrew with a grub/set screw to make it more flush fitting in the focuser and your eyepiece case.  If you do this, you don't need to limit yourself to 2" eyepieces.

Here's an image from CN showing exactly this with Tele Vue eyepieces (along the bottom edge of the image).

Either one would work for your preferences.  The SW 8" 200P, though, is much bulkier to move around and store.  It does come with a 2" focuser which will allow for nice, wide field views.  Overall, the 200P will outperform the 150P, but it really comes down to your preferences for storage and carrying it outside or transporting it to your observing site.

37 minutes ago, iPonchco said:

Thanks for replying and your feed back. 

Learning process and here is my thought process.  I figure since 2" EP do have a wider field of you then I'd want to get to having everything 2".  Perhaps I should have purchased the EP 1st then a barlow. I do wear glasses, so that and a wider FOV was my thought.

I'm still learning, so I wonder if I should return or keep going with my thought.  

2" eyepieces enable a wider true field of view, not necessarily a wider apparent field view.  It's all dependent on the size of the field stop inside the eyepiece that determines the true field of view.  A wider apparent field of view at a certain magnification requires a wider field stop.  At a certain point, that wider field stop may not fit inside a 1.25" barrel.  That is when the eyepiece design must be moved to a 2" barrel.  At some point, even a 2" barrel isn't big enough and a 3" barrel is needed.  Of course, this requires a bigger focuser and secondary mirror which decreases contrast in Newtonian designs.  3" eyepieces are fine in refractors, but you need a 3" diagonal.

Here's a diagram Tom Dey on CN put together to illustrate the field stop limitation of each barrel size.  0.965" was the standard for entry level scopes 50 years ago instead of 1.25".

The takeaway is that 50 degree AFOV eyepieces are limited by field stop at 32mm in a 1.25" barrel, 68 degree eyepieces stop at 24mm, 82 degree eyepieces stop at 16mm to 18mm, and 100 degree stop at 13mm.  In a 2" barrel, they stop at 56mm, 41mm, 31mm, and 21mm to 25mm, respectively.

So, rather than upgrade your 1.25" eyepieces to BST Starguiders or similar for high power usage, you bought a 2" 2.5x Barlow despite having no 2" eyepieces, correct?  You do know the main reason to buy 2" eyepieces is to get wider fields of view than is possible with 1.25" eyepieces, right?  Putting them into a 2.5x Barlow completely negates that advantage because it puts you back in the realm of what is possible with 1.25" eyepieces.

For instance, let's say you buy a 40mm Pentax XW to get to a widest possible field of view.  Good, I highly recommend doing something similar.  It will allow you to take in much wider swaths of the sky than is possible in a 1.25" 32mm Plossl.

Now, you put the 40mm Pentax in your new 2.5x Barlow, and you end up with a 16mm, 70 degree eyepiece that is massive in length, girth, and weight, not to mention cost.  Why not just buy a 16mm Explore Scientific 68° Series or OVL Nirvana-ES UWA-82º Ultrawide eyepiece in a 1.25" fitting?  It would be so much lighter and more compact.  Unless you need the long eye relief due to strong astigmatism in your observing eye (which you did not mention), I can't think of a good reason.

Most people just buy 1.25 2x Barlows because they're cheaper, lighter, and more compact than 2" Barlows.  That, and they tend only Barlow their 1.25" eyepieces to get to very high powers.  What was your reasoning for buying a 2" Barlow?

Have you ever noticed SAEP (kidneybeaning) in your Radians?  It was the first thing I noticed about them viewing through a telescope in the daytime in a shop in 1998 when they were introduced.  It immediately turned me off to them, and I went with Pentax XLs instead which display no SAEP to my eye.

So much for the oft trotted out theory that eyepieces with fewer elements always produces a brighter, contrastier image than that from an eyepiece with a large number of elements.  Perhaps it's true if the level of polish, coatings, and glass purity are similar between the two eyepieces, but so will be the prices (e.g., Tak TOA vs TV Delos).

I'm surprised no one has mentioned suitcase or travel Dobsonians built by ATMs as among the best travel scopes.  Select "travel dobs" on the ninth line down on the left.  I can't get the direct link to work.

The only DSOs that benefit from higher powers in my experience are planetary nebula and globular clusters.  Do these interest you a lot?  The 2.5x Powermate would yield 9.6mm with your 24mm Panoptic, which is a decent mid-high power combination.  I tend to favor a bit lower focal length eyepieces, in the 12mm to 14mm range, for viewing most DSOs in my f/6 scopes.

What focal length eyepieces did you sell?  Which of them did you tend to use the most often?  That should probably be your guide to purchasing replacement eyepieces.

If you can get double-duty out of a Powermate, then I say go for it.

Exactly why would it make more sense to mount a scope on top rather than on the side of the mount?  On an alt-az setup, you'd have to counterbalance a scope on top to keep it from turning the whole mount turtle at high altitudes, adding unnecessary weight to a grab and go rig.  Mounting it on the side allows it to be balanced front to rear at any altitude without any additional weights.  Here's my dual mount grab and go setup with a Mak side mounted on one side:

Try looking at distant (1/4 mile or further) object during the daytime or wait for the first quarter moon at night.  Take the eyepiece out of the focuser and look at the aerial image in the focuser from a distance of a foot or so.  It's sort of like looking in a shaving mirror.  Does the object appear sharp?  If so, we'll assume you have a good mirror.  Next, on the moon at night, put a couple of strips of frosted tape across the empty focuser tube center and see if you can bring the moon to a sharp focus on them, sort of like focusing on ground (frosted) glass plates in view cameras of old that were then replaced with a film plate.  Next, lock the focuser (there should be a thumbscrew on the side of the outer tube for this purpose) and remove the tape.  Last, put the 30mm eyepiece in the focuser and see if the image in the eyepiece is nearly in focus.  Unlock the focuser tube and slowly start moving the focus wheel forward or back, depending on which way causes the image in the eyepiece to get smaller and less fuzzy.  At some point, it should razor sharp.  If it doesn't ever reach a sharp focus and instead starts getting more bloated again past a certain point, you've either got collimation issues or a really bad figure on your mirror.  I doubt that your eyepiece is to blame.

If you can't ever get a sharp image of the moon on the frosted tape, note at which position of the focuser the image is smallest.  If it is all the way in/down, you'll need to move your mirror forward/upward in the main tube to push the image further out the side of the tube.  If it is all the out/up, you'll need to add an extension tube to reach focus.  You also might be able to get away with not inserting the 30mm eyepiece all the way in the focuser when trying to focus with it.

If you can't ever get a sharp image at 30mm, forget moving up to 9mm.  It will only get worse.

5 hours ago, FLO said:

You don't need to believe us Louis. It is okay. VAT doesn't affect you in the US 🙂 

Steve 

Unless I want to buy used from the UK and have to go through all this again to convince the seller than it's 65% of the pre-tax price. 🤣

I have bought used from Australia with no issues, and they also have VAT (10%, though, so about the same as our sales tax).  The asking price was about 75% of new, but the item had a 9 month lead time, minimum, if new, so I was happy to pay a premium for it.  No customs (less than $800) or sales tax (out of country) via AustPost/USPost.

Getting way off topic now, but I just wanted to point out that UK VAT rate has changed over the years according to Wikipedia, and I didn't hear about raging protesters in tactical gear sacking Parliament for any of them:

Standard VAT rates since 1973:^[40]

*During this period an alternate VAT rate of 25% and then 12.5% was introduced for petrol and some luxury goods.^[41] This was abolished in 1979.

18 hours ago, jonathan said:

One of the other handicaps is the tripod - I have the Horizon heavy duty tripod, it may be more than is required for the Skymax 102 but the weight of the 102 makes it feel a little more 'weighty' to quickly and smoothly pan to follow a bird in flight at high magnification, there's also some wobble from my shaky hand / arm control.

Invest in a good fluid head normally used for videography.  The pan and tilt motions will be smooth and well dampened.

18 hours ago, jonathan said:

The narrow field of view is definitely going to make finding the moving target more difficult

Add a 6x30 straight through finder scope or similar to help get the scope quickly on target and then switch to the main scope's eyepiece.

18 hours ago, jonathan said:

Also the focus knob on the Maksutov design is inconvenient for refocusing on the fly

Can't help you there.  It's the nature of the beast.  I don't think there's room on the back for even a 1.25" Crayford focuser on a 102.

Try the 5x Barlow with the 25mm in the interim to see if the image is improved over the 10mm with the 2x Barlow.

You have checked that your scope is properly collimated, right?

Have you been able to observe the rings of Saturn?  They should be pretty obvious.

Personally, I don't like using Barlows or "magnifiers" like the Powermate unless it stays in the focuser all night.  It's a pain to insert them between the eyepiece and the focuser and to adjust focus afterward.

The 9mm Morpheus is very close to the 10mm Delos in performance in my experience, so I can highly recommend it as a lower cost alternative to a TV eyepiece.

The 10mm and shorter Pentax XWs are also a good TV alternative.

If you like 100 degree views, the APM XWA HDC line is also a good TV alternative.

At 30mm, I recommend the APM UFF once you've returned the borrowed Nagler.

There's also the BCO line for planetary observing.

You haven't really established a budget or preferred objects to observe.  You haven't even stated whether or not your mount is driven or not.  All this makes offering advice difficult.