parallaxerr

One thing I have noticed which may sway the decision: 

When considering what I know to be a good exit pupil for observing from my location, the extra focal length of the 10" does offer a larger image but also starts to really draw in the FoV available with my current EPs......that could get expensive not only in wider field EP's but a coma corrector too.

Am I right in saying that using moderate 55°-68° EP's with the 8" would not necessitate the requirement for a coma corrector?

Over recent months I seem to have come around to the idea of a reflector. I've previously resisted having just accepted that I like fracs, but I am guilty of never having owned a newt (I did once have an SCT though).

Maybe it's the realisation that large refractors are just too much of a compromise or that having recently collimated a refractor, realising that it's not really a big deal. Ironic that I had to do that when it was collimation that put me off reflectors for so long. Also, there's no arguing with the £/inch of aperture equation!

I also now have a capable mount in the form of the AZ100 so I've been looking at OTA sizes and weights whilst trying to keep aperture fever at bay! 

It would appear that both 8" and 10" newts are being used on similar mounts, such as skytee II's, but the 10" don't half look big! It's so difficult to tell from some images where there's nothing to scale against though, as people often take photos of their kit in isolation. I have used the threads below for comparison...

This is purely a DSO venture, though I'm sure both would perform admirably on planets. My winter targets typically being the Veil Nebula, Orion, Andromeda, the Ring nebula, etc. I'm really interested to see how much deeper I can go with a larger scope and to find some new targets, having not ventured beyond 120mm aperture before (apart from the 8" sct but that only really got used on Jupiter at the time).

Can anyone comment on whether the additional size and weight of the 10" is worth it over the 8" for the extra light gathering ability? A subjective question I agree, but I'd be interested to hear anyway, e.g. "the 10" doesn't offer much more but is a beast to handle", or "the extra 2" makes a HUGE difference to what you can see".

Also, I wonder if the 10" is going to offer any more from my home location with moderate LP, or if it's just going to collect more of the wrong light? Is there a point where this becomes an issue with respect to aperture?

An OVL 27mm extra flat EP. Nicely finished but of kit with a lovely large eye lens. 

1 hour ago, Don Pensack said:

JUST BE AWARE THAT THE 27MM IS A 53° APPARENT FIELD.  THE 24MM APM IS 65° (CLAIMED, 63° MEASURED).

Hi Don, thanks for confirming 👍. I did realise that and saw it as middle ground between the Tak and RKE. 

Now, if someone could make a 28mm 68° 1.25" ep, I'd be most grateful 😂 

Thanks for the info @Louis D, I've seen your posts like this on CN and they're very helpful!
 

By way of an update, I ordered the OVL 27mm Extra Flat as it seems to strike a nice balance between price and FoV, hopefully it will be comfortable enough to use for extended sessions. I'm hoping it will be of similar performance to that APM 24mm, nice and flat.

4 minutes ago, John said:

Good stuff Jon !

Many of the lower cost refractors that I've owned have required colimation to some degree. I use a 2 stage process: focuser optical axis first (laser colimator for this) and once I'm happy with that, the tilt of the objective with the cheshire as you have done.

Hopefully you will see some benefits in the views in due course

 

 

I'm just glad I got the Celestron with the collimatable cell! Had it been a SW I guess I'd have been stuck.

Will invest in a laser too I think. I did my best to align the focuser with the collimation ep, but there wasn't quite enough adjustment in the 3 screws to get it bang through a full rotation, but it's only a smidge out with the focuser at 180°. Having said that I rarely rotate the focuser any more as I mount the scope lower and the collimation is spot on with the focuser upright. 

I also checked with the diagonal in and there was no change, so hopefully I've achieved alignment throughout the full optical train.

I took about a bit of astro fettling last weekend, my primary goals were to flock the dew shield of my 120mm f8 achro and to do something about the red diagonal I have which really doesn't match the scope.

The diagonal turned out well, a bit of adhesive vinyl and a black paint pen have transformed the exterior whilst the inside got the gray foam side pads replaced with flock. It appears much darker to look through now, hopefully a bit of extra contrast?

Whilst removing the dew shield to flock though, I soon became aware of a rattly objective. I know this is no major cause for concern normally, however it sounded too loose for my liking. I fashioned up a tool to loosen the objective lens retaining ring, which oddly was very tight. After standing the tube on the focuser end and doing the tube tap dance, I gently nipped the ring back down to snug up the lenses.

All week though I've been concerned that the scope may be out of collimation so did a bit of reading up. It turns out the scope was supplied with a collimation eyepiece which I had kind of disregarded thinking it was a standard accessories pack and the collimation ep was likely meant for a newt. Up the attic I went to recover said ep.

Having performed a preliminary inspection with the collimation ep I discovered quite a bit of mis-collimation. Two donuts were visible as expected (reflections of the lens surfaces) however they were only about 50% overlapped, i.e. far from concentric. Fortunately the OMNI XLT 120 had a collimatable lens cell so I took the plunge and got the tools out, only to discover more "looseness" in all but one of the collimation screws. 

Interesting that previous start testing returned reasonable results, though very soft rings I thought. This meant I had to test very close to focus, perhaps this hid the mis-collimation as racking further in or out just produced colourful blobs.

An hour or so of fettling, including focuser alignment and I seem to have a nicely collimated scope now! Initial daytime observations seem to indicate a fair reduction in CA which I always though was a bit high in this scope. It may also go some way to explaining the poor performance on Mars recently.

Of course a repeat star test is now required, but the forecast suggests I won't be doing that any time soon! Really looking forward to and hoping for some improvements during the next session!

I've added a photo of the view through the collimation ep after adjusting but it's hard to make out the pattern. Suffice to say it was nowhere near round before!

Thanks Ruud, that's how I understand it. One negative I'm picking up on is the effort required to hold the specific position to achieve the effect, which may be less than ideal for longer sessions.

That Pentax looks interesting Martin, never had one. Looks like a wanted ad would be required there.

The reports of the RKE floating effect are certainly making me think hard about this one!

Sounds good John, reviews seem mixed but nothing really bad and mostly liked. Certainy in no rush judging by the weather forecast!!!

Hi John,

It's to go in the F8 achro.

Hadn't seen the OVL EP as I was searching 28mm but 27 is close enough, thanks for the link. In fact 27mm nails the exit pupil target, I was just splitting the gap at 28mm.

Do you have any experience of the OVL 27mm?

I'm on the hunt for a 28mm eyepiece to fill a (probably psychological) "hole" in my collection, between 24 & 32mm. A 28mm EP would give me an exit pupil in my current scope of ~3.3mm, which I have found in previous scopes to be favourable for DSO viewing in my local skies.

Well, there's plenty of 28mm EP's out there you may say, but here's the clincher; I want to stick with the 1.25" format to avoid the associated on-cost of 2" accessories and filters. Lots of searching has resulted in the EO RKE Erfle and TAK MC Erfle being the only readily available options.

Whilst the TAK has an extra 15° of AFoV, I read that edge correction is poor. Conversely, the EO RKE has only 45° AFoV but is supposedly sharp to the edge and is said to have a particular floating effect that is "magical".

The TAK comes in at circa £210 with the RKE @ £72.

Has anyone compared these eyepieces to make a subjective comparison?

Are there any other 28mm 1.25" options I'm missing? A 28mm plossl would be ideal, but no luck finding one.

Cheers all,

Jon

15 hours ago, John said:

Mars looks OK'ish at times with the 90mm achro refractor I popped out tonight. The S polar cap is clear and a range of dark areas when the seeing and the wind gusts steady for a moment and the cloud blobs keep clear. Not staying out for long though.

 

 

What time were you observing John. It looked like conditions were improving when I packed up, but couldn't stay up later what with the kids having me up at 5am 😴

Could be heat radiation/thermals I was suffering with. I may have to plan a later session to get better views.

Well, what a disaster. Just pulled my gear in after an hour of dreadful conditions, worse than previously seen. Attempting to view the planets was like looking at a photo of them through a running stream. At least now I know it's not my scopes!

Thanks everyone for the input. It's great to hear the opinions of more seasoned observers and those with different and superior equipment.

It definitely sounds as though conditions are more to blame than the scope! For a bit of fun, I've dug out the Vixen 80mm achro for a side by side comparison when the clouds part. I'm wondering if the dimmer image and less CA will clean things up a little. I seem to be limited to less than 150X, so the Vixen should hold up to that.

I'm wondering how observers in the South West/South Wales region have been getting on with observing the planets recently?

I've been finding it hard work with my F8 achro and can't quite fathom whether it's the local seeing or the scope. Star testing suggests collimation is good, though the soft extra focal image may suggest quite some under correction, can this adversely affect migh mag work?

Jupiter has been very washed out, I can just about make out the North and South banding and a few rare glimpses of the GRS. However, I seem restricted to quite low magnification, in the region of X100, any higher and the image becomes mush.

Saturn is handling a little bit more mag as usual, but again nowhere near what I'd expect. The Casini division is fleeting at best.

Mars, well South polar cap and the faintest hints of albedo, which may sound OK but I've seen so much better in the past in other scopes.

Of course, the planets are low and conditions are likely considearbly different to past observations. I've noticed a lot of bubbling when in sharp focus suggesting it's mostly atmospheric issues.

So, before I find reason to buy a planetary scope, please tell me others in the region are experiencing the same!?!?

I had my first planetary session with the AZ100 last night. I had previously been concerned about vibrations but I'm happy to report that my concerns were unfounded. With the 120mm refractor nicely balanced and the alt/az clutches both lightly tightened, I found I could move between Saturn and Jupiter with ease. I then switched straight to the slo-mo controls which, with a light touch, proved to be exceptional at keeping both targets in FoV. As I was observing near the meridian, I only really had to track in Az.

I'm very happy with the result and it has given me confidence that the mount would take a 150mm refractor with ease, something that I have been considering....

1 minute ago, omo said:

A local machine shop would be able to drill and tap your existing saddles, you would get the dimensions from the handle bracket when you recieve it, save a bit of $, or @Dek Rowan Astro may be able to provide those on a drawing to you?

That's a great call. The good news is the base design of the saddle doesn't appear to have changed, so there is enough material there to accommodate the new holes. All you need is the hole pitch then it's a 10 minute job with a drill and tap

1 hour ago, mikeDnight said:

Lockdownmas presents lately have been mouthwatering Japanese classic 5mm and 20mm Ultrascopic eyepieces in pristine condition, and a secondhand copy of Bureaucrats - How To Annoy Them, by R.T. Fishall (Patrick Moore). 

Now that is a book that could come in handy where I work 🤬

....Oh, and nice EP's!

1 hour ago, johninderby said:

1. Ah good old Trichloroethylene. 😬

That's a good score. Still got a drab of this in the garage, makes an excellent cannon propellant...

1 hour ago, KevS said:

Trichloroethylene was one of my favourites.

1 hour ago, Davey-T said:

Used to have a large tank of that at a place I worked at in my youth, had gas burners under it to produce a degreasing fog, it had a water cooled ring at the top supposed to keep the fog in the tank but it fought a loosing battle, nice Victorian factory, no ventilation, fumes were great for getting high on, exposed extremities went numb after a while, ah elf and safety where were you when I needed you 🤣

Dave

Aah many a clean cylinder head emerged from the trich bath!

3 minutes ago, johninderby said:

Boring grey and doesn’t smell. 🙄

Bought it now as it’s hard to find the small packs of it. No problem if you want a pack big enough to do your 737 though.😁

Yes, very dull stuff. Not like the nostril-ripping, skin peeling aircraft lubricants from back in the day....I still have the scars and get the occasional whiff 🤣

Most of the fun stuff we used to play with is banned now!

 Nothing too exciting, just a little upgrade to the Omni in the form of some CNC tube rings bolted to a Farpoint Losmandy dovetail. Safe to say that in combination with the AZ100, it's all rather sturdy now!

1 minute ago, johninderby said:

Ypu could probably do an EQ6 mod to the tripod similar to the one I did to a Berlebach.

 

Yes, I've already eyed that up John. All it needs is the centre bore machining out by a small amount and the centre hole clearing and re-tapping to M12, as you did. Then the AZ100 would drop straight on.

I'm inclined not to though. I'll keep the steel tripod as is so the 16" extension can go back on with the AZ4" for a smaller grab'n'go setup (once I've acquired a BB that is!).

Just managed about 15 minutes on the Moon before the cloud swept in. It would appear that the shorter pier has drastically improved the situation, any wobble/vibration is now very short lived and far less in magnitude than before. A sharp tap to the tube or mount results in one or two oscillations that dampen out in about a second.

At X200 I could track in Az using the flexible slo-mo control whilst still being able to scrutinise fine detail, so I think the setup is good for some high mag action on Mars later in the year.

I tried the mount with the tripod collapsed and raised up by about 50% on the legs, no difference. This tells me any remaining vibes are still in the shorter extension but I can't try without it because the tripod is an EQ5 fitting and the AZ100 is EQ6 - the extension is essentially an adapter between the two. I've also changed the knurled knobs back to the socket cap screws which can be tightened a bit better, removing any play. There's no need to break the mount down now as it's lost a fair bit of weight and can be carried relatively easily.

All in all very happy, a success. Yes a Berlebach without the extension would probably perform better and is still desirable, but has dropped down the priority list a little now!