Louis D

If you can come up with a way to replace that tall 1.25" adapter with the filter wheel, it should be doable.  I can't do that with the low profile focuser on my Dob, though.  I have only 25mm of backfocus from the top of the focuser housing.

For someone starting out in visual astronomy on your apparent budget, I would recommend the GSO 6 inch DOB Telescope.  It's a slow mirror, so figure and collimation aren't so critical.  There is no CA at all.  You can get by without a coma corrector as well at its f-ratio.  The Dob mount is rock solid stable compared to any budget Alt-Az or EQ mount.  The viewing comfort is nice with the right adjustable observing chair.

The only reason to not recommend it is its storage and transport size.  If you plan to take it on mass transit to get to your observing site, I would instead recommend a 102mm or 127mm Mak on an alt-az mount to avoid counterweights.

4 hours ago, Jim L said:

Louis, in the 10” size I’m interested in the Apertura costs $950 and is on back-order, while the SkyLine costs $900 and is in stock.  The only difference I’m able to find is the Apertura includes a 35mm extension and the SkyLine does not.

https://www.highpointscientific.com/brands/apertura/apertura-ad10-10inch-dobsonian-telescope-ad10?rfsn=6699648.e10fc93&utm_source=bing&utm_medium=cpc&utm_campaign=380212636&utm_content=1241348818236351&utm_term=highpointscientific&msclkid=ef3beb05fcfd1c6d63fa8f70d68135fc
 

https://www.telescope.com/SkyLine-10-Dobsonian-Reflector-Telescope/p/113095.uts

Sounds like a plan as long as Monica is aware of the assembled weight and bulk.  10" Dobs are starting to get on the heavy/bulky side of things.  I think it breaks down into two major pieces fairly easily for transport.

29 minutes ago, Spile said:

It looks as though the Orion Skyline is the same as the Apertura AD8.

It is.  I can't quite figure out what the extra $100 for the Orion Skyline version buys you over the Apertura AD8 version.  Both have free shipping and charge sales tax.  The accessories are basically identical except that the AD8 includes a cheap moon filter.

Don't overlook the Explore FirstLight series.  Their altitude trunnions alone make them very worthwhile.

And all of those stars that you can see are strictly within the Milky Way galaxy, our home galaxy.

On top of that, only about 3000 to 5000 of the billions of stars in the MW are visible to the naked eye, and most of them are relatively near to us.

On 27/05/2023 at 04:45, Mr Spock said:

Yesterday I ordered a darker blue and a violet filter. I'll see if they make a difference.

I would think a pure blue filter like that used for RGB color separation coupled with a variable ND filter would be ideal for experimentation.

21 hours ago, Jim L said:

There were a couple of other large reflectors at the party, including a 14” Meade Schmidt-Cassegrain, but the big Orion out performed them handily, being brighter, having more contrast, and being sharper both on and off center. Honestly, I was surprised by how much better it performed than it’s far more expensive peers, but perhaps their mirrors were dimmed by age, and their collimation wasn’t optimal. I don’t know, but I was very impressed with the Orion 12” Dob.

That's why I bought a Dob as my first scope.  I went to two public outreach star parties in the late 90s.  There were about 40 to 50 scopes on the field each time.  Each time, I was most impressed with the views through the mid to large sized Dobs as compared to the views through the A-P APOs and SCTs on the field.  I won't lie, those A-P APOs sure looked pretty, but 10" to 18" Dobs totally blew them away on nebula, globs, and planetary detail under our Texas skies.  The larger SCTs all had mushier views than the equivalent sized Dobs.  They all couldn't have had bad collimation.  It was only with the recent arrival of the Celestron EdgeHD SCTs that I thought planetary views rivaled their Dob counterparts.

On the same night of good seeing at these parties, I can easily pick out more detail aperture for aperture on planets in custom Dobs having hand figured mirrors over commercial mirrors.  That, and the mirror cell, focuser, and motion mechanics are so much better.  You would think the commercial suppliers would be trying to up their game after 25+ years of making Dobs, but they're not.  I think the mirrors have improved in quality, but not the mechanics.  They're still using heavy materials with poor sticktion/friction balance.  Where are their premium offerings to compete with the custom makers?  Toyota created Lexus to successfully compete with the luxury car brands.  You would think the Asian telescope makers would follow suit with a luxury astro brand to take away market share.

That's wild that it needs 20 pounds of counterweights, especially when the lower tube assembly already weighs 50 pounds.  And what's up with the weight of the groundplate assembly?  That's crazy heavy.  And here I thought using oak instead of aluminum was a heavy material choice.  Why use steel?  Because it's cheap and strong?

Why are commercial truss goto scopes so heavy?  Starmaster's old Sky Tracker system only added 11 pounds to the rocker box (including gel cell).

3 hours ago, Whistlin Bob said:

It's not an elegant or pretty machine, and at 80kg you wouldn't call it grab and go. But the performance is terrific 😃

And here I thought my 15" Tectron truss Dob was heavy at a little over 100 pounds.

7 hours ago, PeterStudz said:

I’m not a fan of the lazy Susan bearing type things. And I tried to find the above wall panel stuff in the UK without luck. But this -  stucco embossed aluminium - worked really well for me. Cheap too. I paid £13 for a 50cm (20 inch) square from a local sheet metal supplier. Lager sections are available. And easy to cut with tin snips.

Works well for altitude bearing plus Teflon too. 

Good find.  Basically, you just need to find a hard, nubby surface that is glossy.  The finer the nubbiness, the higher the sticktion (more contact points to overcome static friction) and the smoother the motion (like driving on a finely rutted road vs. a potholed road).  The bearing surface area of the Teflon blocks also plays into the whole motion equation as well.  Larger blocks will play better with larger nubs by spanning multiple at once.

There's definitely an art to it based on materials availability and matching them up properly.  For instance, nylon furniture glides may work better than Teflon blocks on certain surfaces.  You just have to experiment to find out what works best.

3 hours ago, Jim L said:

A couple of days ago we had a brief pause in the storm and we wrestled the Dob through the kitchen and into the back yard. The seeing was atrocious and so I wasn’t able to evaluate collimation or optic quality, but we were able to wrestle the big Dob in the general direction of M13. When I say wrestle I’m not kidding.  It took tapping, shoving, rapping and banging to move the Dob onto M13, and more tapping, shoving, rapping and banging to keep it there. The Teflon azimuth bearings were by no means up to the task, the stiction was horrendous, and Monica and I were both frustrated and disappointed by how poorly the mount performed. I asked Monica whether she was still in love with the Dob and she sadly confessed that much of the shine was lost.

I felt bad for Monica, and I want her to have a great experience at the star party, but nothing I did after our short observing session seemed to help make the mount livable. That is until I remembered a trick one of the regulars at CloudyNights mentioned: Ivory Soap. I removed the scope tube, flipped over the mount, and rubbed the Ivory bar soap liberally over the bearing surface. Initial indications are that the soap’s made a huge difference in reducing stiction, but the final test will be Friday night at the star party. Fingers are crossed for favorable weather and a successful night with the Dob. We’ll see.

Try surfacing the bearing surface with Fiberglass Reinforced Wall Panel in a nubby texture.  It should be glossy to have low friction, but fairly coarse to reduce stiction.  You can run a piece of Teflon across it to get an idea of the feel of it.  I won't lie, it can sound a bit like rumble strips on a highway when rotating the scope, but it works great.

Short of using a perfectly cleaved crystal surface or a vacuum sputtered crystal surface, a Herschel wedge's uncoated first surface mirror should yield just about the smoothest, lowest scatter diagonal surface possible.  And, unlike a prism diagonal which has a similarly smooth surface, there is no possibility of introducing chromatic aberrations into the image.  Thus, it probably would yield the highest contrast possible for ultra-bright objects short of straight through viewing.  Of course, with straighter through viewing, you'd probably have to introduce some sort of dimming filtration, and that could add scatter itself.

For those not familiar with the internals of a Herschel wedge, I've attached a Wikipedia diagram below:

Try contacting John Chen for Svbony questions.  I was contacted by him in regards to customer input for the 3-8mm zoom while it was still in development in January of 2022.

Here is his contact information:

sales manager of eshow co.ltd including 3 brands( retevis(ailunce)/Retekess/ svbony)
Skype: john51888@outlook.com
Facebook:John Chen
paypal em-ail: eshow.btoc@gmail.com
whatsapp:+8613526737346

And here was the ebay email address that he contacted me through:

svbony_lq5848lh@members.ebay.com.hk

He clearly wants Svbony to be a quality company that responds to customer interests and needs.

4 hours ago, RyanL said:

Hi,  Am I right in thinking the larger exit pupil is better for glasses wearers like my son?

Thanks..

Nope.  Longer eye relief is better for astigmatic eyeglass wearers.  If your son's prescription has little to no cylinder (CYL) correction, he doesn't need to wear eyeglasses at the eyepiece.  You can just focus out the distance correction with the focuser.

Larger exit pupil makes extended, diffuse objects like nebula and galaxies brighter by concentrating the total light flux into a smaller area.  Thus, more photons per unit area increases the perceived brightness.  It also makes the sky background brighter (for the same reason, it's an extended object), sometime negating any advantages (both get brighter at the same rate).  An exception to this is when using line filters like OIII filters on nebula.  The increased exit pupil makes the dim image easier to see because it blocks the light pollution of the background sky while letting through the OIII emission lines.

I just received an affordable 600nm Shortpass filter.  It has a broad, high transmission passband for wavelengths shorter than 600nm and a sharp cutoff very close to 600nm.  Visually, it cuts out practically all red without noticeably dimming the view.  Below is the manufacturer provided transmission graph:

I paired it with my Yellow #12A, Yellow #12, Cheap Yellow, and Yellow K2 (#8) filters when viewing Venus through both the ST80 and ST150.  The best view was the combination with the Rokunar Yellow K2 cutting all violet/blue and orange/red fringing in both scopes.  The color was a pale green without much blue or yellow secondary cast.  The Meade Green was still showing the better image due to the narrower passband, but the intense green color was hard to get past.

I'll have to try out the various combinations on DSOs as skies and time allows.  I'd like to see if a high transmission combination (better than 80%) can be successfully used on brighter DSOs to sharpen star images without losing dimmer components at the same time.

Below is an update to my spectrograph image comparison showing the clearly higher transmission of the 600nm Shortpass filter and its combinations as compared to the Cyan BG39 filter and its combinations.  That, and the cutoff is tremendously sharper at orange-red than anything else I have.

The 600nm Shortpass filter is a work in progress because it is a square piece of glass that I hope to be able to cut 27mm and 46mm circular disks from for 1.25" and 2" filter housings, respectively.

50 minutes ago, jetstream said:

For me, I use the sight tube, then a Glatter laser to line up the sec on the primary and then the Catseye cheshire for primary collimation.

Pretty much the same for me except that I use an AstroSystems laser instead of a Glatter laser and a Rigel Aline for the primary collimation.

For the big truss Dob, I use the laser while working at the back of the scope to get the primary return spot coincident with the outbound spot on the face of the secondary to get it pretty close before checking with the Aline.  I don't have 6 foot long arms to adjust the primary while peering into the Aline at the secondary cage mounted focuser.

For GnG, I would get a 102mm or 127mm Mak.  They are very sharp on solar system objects and good for DSOs under 1 degree in size.  They are rugged, compact, lightweight for their aperture, and hold collimation very well even after being roughly transported multiple times.

If you insist on a refractor for GnG, I would recommend a 70mm or 72mm ED.  They are quite compact, and yet will show larger DSOs and solar system objects quite well.  If you want the best high power performance, spring for an FPL-53 version.

90mm to 102mm achromatic short tube refractors are still going to be big and bulky, just somewhat lighter than their ED/APO counterparts due to lighter weight construction.  However, the color on solar system objects and brighter DSOs will probably displease you since you've been using an ED refractor for some time.  I've been tinkering with filters to subdue the false color, but you end up with a yellow or green image for brighter objects to get a sharp image.  The unfiltered false color doesn't intrude much below about mag 2 to mag 4, depending on your sensitivity to violet light.  Thus, if you're only into faint DSOs, it might not matter much to you.

Another option might be a Heritage Newtonian in either the 130mm or 150mm size, but mounted on an alt-az setup using the dovetail.  I don't have experience with them, but they seem to be well regarded here on SGL and elsewhere.  Just be aware that the helical focuser can be a bit of a work in progress and doesn't play nice with zooms.

I did buy a 6" f/5 GSO Newtonian with dual speed focuser, and I can say that they are hands down a far better all around performer than a 6" short tube KUO refractor which I also bought for comparison.  That, and the Newt is about half the weight and is much easier to mount and use standing thanks to the eyepiece being at the top of the tube.

I suppose if you dropped down to a smaller diameter Newtonian like the SW 130P-DS it might be compact enough for GnG without sacrificing the dual speed focuser.

Howdy from Texas!

2 hours ago, Mr Spock said:

Whatever that is, it doesn't look anything like mine 

I'll say again. the action on mine is perfect. Really smooth and easy - holds a 42mm LVW perfectly.

There seem to be several GSO 2 speed focuser models.  Mine has to be the worst.  It does work once adjusted properly, but I have to remind myself not to touch the tension knob despite the tension being a bit on the high side for lighter eyepieces.  It's set as low as I can go without having the focuser tube drop under the weight of heavy eyepieces (e.g., ES-92 17mm).

Since the moon is basically monochromatic, try using a #56 Green filter to cut the poorly focused violet/blue and red ends of the spectrum.  It will dramatically sharpen up your views.

12 hours ago, VNA said:

Hello, sorry, that is a lot of money, I bought a GSO focuser, 2 speed that works great on my lowly CR6.
It is a 2" and rotable  focuser for about $200.00! It fits perfectly, yes it is Chinese, but in the dark you can't tell. ;- )

5 hours ago, John said:

I have used those GSO units as well and they do work just fine 🙂

4 hours ago, Mr Spock said:

The GSO on my Dob works perfectly.

I have the GSO Linear Bearing focuser on my GSO 6" f/5 Newtonian.  It barely works depending on the tension setting.  Too little, and the focuser tube just drops into the focuser under heavy eyepiece loads.  Too much, and the action is heavy and sluggish.  It's difficult to find the Goldilocks setting in between.  It shouldn't be that hard.

There's a dedicated thread on CN detailing why this is so.  It's clear it was designed to a meet a certain price point.

1 hour ago, Space Cowboy said:

Not sure if FLO are stocking these yet but the mount looks nice. Just tell the neighbours it's a lightening strike and you'll be good 👍

 

OMG, I can think of a lot of other uses for that laser cannon, none of which can be mentioned here due to TOA rules.

3 hours ago, Space Cowboy said:

Dark skies are sadly a thing of the past in Cheshire East. The amount of new housing erected over the past 5 years is unreal. Most of it on prime farmland.

The only dark horizon is towards Shropshire.

Same has happened with me over the past 30 years.  There are now 10,000 new homes, two car dealerships, two tollways plus their interchange, a high school with football field (Friday Night Lights), and multiple giant shopping centers.  I've gone from Bortle 4 skies to Bortle 6/7 skies during that time.  All of it built on blackland prairie farmland.

6 hours ago, neil phillips said:

Tree is massive, that saw would make it flatten a house as it went over lol. Not going to happen. I get time for about one capture, at one location. Then it hits a roof. (All set up on concrete inches from house walls)

Or longer in the garden, as its getting low in the sky. dropped below branches. Under good seeing the low location. Might be worth trying again. At least i don't lose it after 5 minuets. But trying to snatch it as seeing is worsening is not something i enjoy. But we shall see  Morning rising will be better.

Since our neighborhood trees have matured, I've lost all but my south facing view from my backyard.  Our ice storm this winter did take out a huge chunk of a neighbor's tree opening up more of my southerly view, though.