wulfrun

48 minutes ago, CraigT82 said:

I *think* it might be possible, looking at the pics of how the motor attaches - by a single bolt - to simply rotate the entire motor around the fixing bolt to make the new 12t gear mesh with the existing 60t gear?

Good idea, I'd overlooked that possibility. I'd say there's a strong chance a RC car/truck motor pinion would work, assuming you can find the right pitch. It's probably standard so you may be in luck. You'll need the pitch and the motor-shaft size information.

You need a pair of gears in the right ratio AND size and tooth-pitch. You can't just swap out the 24t for a 12t because it'll be smaller and won't mesh (stating the obvious, I know). Might be worth looking to see if radio-controlled models would source something suitable. What type of motor is it? It should be feasible to make the motor run at half-speed too.

As a relative newbie, I've never seen Albireo in a scope. It's not well placed for me until rather late but I've found it, visually, before now. Last night was clear until early hours and I really have wanted a look at it. The seeing wasn't very good but I was determined to have a go. Not having aimed a scope at it before I had no idea of what magnification it would need either.

Being a late decision to try for it, I popped the Heritage 114P out and took the Hyperflex 7.2-21.5mm zoom and my newly-arrived BST 5mm. I waited until Cygnus was above the murk (nearly midnight) and managed to place Albireo in the RDF. In the Hyperflex it became apparent that high mag isn't needed but I tried the BST anyway. Well, it's new-to-me so has to be done!

The BST did darken the sky a lot and provide a beautiful view (as did the Hyperflex at 7.2mm). There were times when the colour contrast was not so obvious, due to the seeing but there were also moments when it was just sheer beauty. I'm glad I made the effort and was suitably rewarded. The BST performed well in the scope, so I'm pleased there too.

A worthwhile exercise and Albireo seen at last, I can appreciate why folk talk about it now!

Postie brought me a Starguider 5mm, courtesy of the classifieds and @AstroNebulee

Credit needs to be paid to him, since RM's "first class" service took 5 days and he pursued them over it.

I had the 150PL slide down the dovetail recently, when aimed near-zenith, clearly not sufficiently tightened. Saved by the limit bolt, not far it could have fallen from that position and onto grass...and it's not a Tak. Ouch, I feel for you!

100% cloud here, dense stuff at that. Agrees with Clearoutside. IF that's accurate, I'm looking at Monday and a bit of Tuesday, which just happens to coincide with new moon...so I'll take that with a bucket of salt then!

38 minutes ago, Pitch Black Skies said:

Cheers wulwrun. Can you send me a link to the ones on FLO? I can't find any blank ones, just empty ones that are pre-cut for intended sets.

Found one on eBay but looks a bit cheap https://www.ebay.co.uk/itm/233484293126

I think waterproof is the way to go.

Yes I think the FLO ones are pre-cut. The one I bought is a ROC, same as the £17.99 one on the Maplin page linked to above.

7 minutes ago, Pitch Black Skies said:

I would like to buy one of these blank foam cases to start my collection. Where can they be bought?

You can find them on FLO, Ebay and no doubt a fair few other places. Look for "aluminium flight case"

Someone posted recently about having bought a "telescope 262 power", asking if it was any good. Not sure if they ever got back to confirm the model, maybe this is the same though.

3 minutes ago, Starwatcher2001 said:

When doing solar observing, please remember to cover up or remove your normal finder. Friend of mine forgot and set light to his hair. 🤣  Could have been a lot worse...

Not sure if it's true but I think I read somewhere Galileo is supposed to have singed his beard?

Could be I'm missing the problem here but...plumbob weight hanging under the mount, fix a circular scale under it somehow. Probably more accurate, cheaper and no batteries required. Feel free to ignore if it's not a practical solution!

20 minutes ago, philj said:

Just watch a few telly programmes and count how many times the words Brilliant, Fantastic, Incredible crop up. Sign of the times unfortunately.

You forgot "iconic" (amongst any number of other hype-speak words)

31 minutes ago, vlaiv said:

There you go - another daytime photography pearl - 1" sensor - has nothing that is one inch long (neither sides nor diagonal - really no dimension that is 25.4mm).

Again, it's from historical comparison as far as I understand. Wikipedia says the 1" format is from vidicon tubes used in early television and the 1" is the tube size not sensor area. I agree the "comparisons" are all somewhat random though and may confuse as much as be useful. However, I think it's handy for a photographer (non astro) to have a yardstick in their mind to use when thinking of composition etc.

I am of the age where 35mm film was the norm for me. I still look at a scene and think of what 35mm lens I'd use, then mentally convert that by the camera's "factor'. It is no different from being brought up on feet and inches then trying to visualise something given in metres, I suppose.

In telescope terms, I don't feel that I'm hampered by being a long-time "daytime" photographer. Additionally, "daytime' is, itself, misleading because I often take night-time shots, some of my best shots are such. Perhaps "terrestrial" might be a better label?

"Long" and "short" F/L may be rather different in the astro world but they are just pigeon-holes.

1 hour ago, vlaiv said:

I've come across bunch of things that daytime photographers use that can be described as intuitive and helpful - but are misleading at best.

One such thing of the top of my head is "50mm equivalent lens" for either APS-C or 4/3 sensor.

What could be equivalent of focal length? And surely different numbers can't all be equivalent to certain focal length?

It turns out that 25mm FL lens is equivalent to 50mm lens for 4/3 sensor and 30.86mm FL lens is equivalent to 50mm lens on APS-C sensor (and bunch of other equivalent FLs ).

As far as I've gathered - photographers primarily think in terms of FOV on 35mm / full frame sensor rather than in terms of actual millimeters of focal length.

50mm on full frame will have same field of view as 25mm on 4/3 sensor or 30.86 on Canon APS-C sensor - that is why they are "equivalent".

Other than that - you are absolutely right, focal length is distance between objective and point where parallel rays bent by lens converge into single point.

Agreed, however the "50mm-standard lens" is historical and relates (approximately) to the 35mm film frame diagonal (it's 43mm in reality). A 50mm lens "sees" roughly the same as the human eye would (although not in terms of FOV). So comparing that makes sense to a photographer brought up on film. The F/L is the only way to change the image size for a given sensor (or film format) diagonal, for perspective, FOV or whatever other reasons. Since 35mm film was the dominant film format for many decades, it made sense to use it as "the standard". Indeed, consider the the so-called full-frame digital camera, the frame size is an arbitrarily chosen one in that is the same as, er, 35mm film. It's not full-frame compared to 120 film, 110 film or any of the other (many)  film formats used. Likewise, micro 4/3rds is "full-frame" equivalent to 35mm half-frame.

Surely the focal length is the (optical path) distance from objective to focal plane? By definition. Matters not if it's a camera or 'scope.

Hmm, I got half the story then @vlaiv. I chose to ignore the distortions aspect since I thought it wouldn't be the major factor.

I'm open to being corrected if my understanding is wrong or incomplete but I'd say it's largely down to eye relief.

The shorter the focal length of a Plossl, the shorter the eye relief. Say you have two scopes, a 1000mm and a 500mm F/L. If you want 100x magnification, you'll need a 10mm EP with the former but a 5mm with the latter. You'll need your eyeball on the lens of a 5mm Plossl in the 500mm scope.

If you use a 10mm EP in both scopes, you'll get only half the magnification with the 500mm one versus 1000mm but the eye relief would be the same.

10 minutes ago, Alien 13 said:

F ratio is a funny thing, useful for determining exp settings but its never a good idea to assume that everything is equal. I could have a f/2.8 DSLR lens or a Phone camera with a f/2.8 lens and it should be obvious which one actually collects more light..

Alan

Correct, but the tiny smartphone lens is a very short focal length and focusing on a tiny sensor, whereas the DSLR lens will be much longer F/L imaged onto a vastly larger sensor. Given equal pixel sensitivities on the sensor (not a given in reality) they do still both need the same exposure for the same scene & lighting.

Thanks @Stu

Yes, that does pretty much agree with what I see, I think I can count it as a "tick". I think having seen it at higher power is what allows me to see it with the 32mm - I know it's there. Had I not spotted it at high power though, I doubt I'd have noticed it otherwise with the 32mm alone. I don't need to use averted vision but it must be fairly close to the limit from here.

As a recent beginner, I don't think I've been out once and not seen at least one satellite - and usually several. The other night I counted 6 times one streaked through the EP view. Considering that my scope sees a tiny bit of sky and I'm looking, effectively, at random areas, it shows how much of a proliferation they are becoming. More common than Lyrids, of which I saw a total of zero last night!

48 minutes ago, Stu said:

Not sure if this helps. I changed the timing until Polaris B was at BC 12 o’clock relative to Polaris (obviously it rotates around the primary over the course of the night).

The second image projects this direction upwards so you can see where is is relative to Cepheus and Cassiopeia.

Thanks for that...question: is the first view as-seen in a newt EP? If so, it is close to what I see. Because I take the RACI off when storing the scope, I've taken to using Polaris to make sure it's accurate before starting a session. I've noticed that this close star is just about discernable even with a 32mm Plossl. It's faint and very close even at high mag. The other one, shown lower-right above, is much more obvious, even though your view shows it less so.

EDIT: what did you generate that view with? I may have to try and generate a view for a specific time and go check if it agrees with my EP view.

On 20/04/2021 at 15:24, Pixies said:

Did you try the double cluster? You can find it by following the chain of stars south-north up from Mirfak towards Cassiopeia.

UPDATE

Last night, I did try and locate this - initially with no success but after a bit of searching I found it! I put the Telrad half way between Mirphak in Per and Ruchbah in Cas, then used the RACI. Not only found it and had a good look, I managed to re-locate it a couple of times later on, so I'm pleased I can re-find it now.

I also had another go at epsilon Lyrae and had a similar result. I managed a varying resolved/split using a 20mm + 2x focal extended (x120) with the southern (upper in EP) pair splitting more clearly and more often. I might have done better later on when it would've been higher but I didn't try.

35 minutes ago, Second Time Around said:

These dual 1.5x/2x Barlows allow the black lens cell to be unscrewed from the body of the Barlow and then screwed into the filter thread at the bottom of an eyepiece to give approx 1.5x.   First Light Optics do one in their Astro Essentials range that even has a standard T thread at the top for attaching a camera.  It's just £25.  Go to https://www.firstlightoptics.com/barlows/astro-essentials-125-2x-barlow-with-t-thread.html

I feel it's worth pointing out that there are some incompatabilites here, depending on which zoom/Barlow you pick. I have the Baader Q-Turret (x2.25) barlow, with removeable barlow lens group. However, the lens group needs a recess to screw into and this space is occupied by the moving elements of the Hyperflex 7.2-21.5 and SVbony 7-21 zooms so it cannot be used this way. Just felt it needed to be pointed out that not all zoom/Barlow elements combination are possible, it needs to be checked. The Astro Essentials Barlow you mention does look as though it will work, however.

Oddly, you can remove the negative elements from an ES 2x focal extender and they will fit in the above zooms, although I have no idea if the optical train makes sense that way.

2 hours ago, Louis D said:

So the mere act of owning or taking delivery of a >1mW laser is an offense under this statute?  The mere act of pointing a laser to the sky is an immediate offense?  How many people were arrested for having those Christmas laser light shows missing the side of the house and pointing into the sky?  I read of a lady in New Jersey who was issued a warning when hers got knocked over backward and was lasing nearby planes.

Not so fast, this is the UK! Some of our laws aren't straightforward. There are things you can own legally but not buy legally, things you can buy legally but can't be sold legally and a lot of wierd variations. I think lasers (pointer type) over 1mW fall into "legal to own but not use without good reason" category, although I'm no expert. Pointing any GLP skywards and being noticed tends to invoke the "arrest and ask questions later" response from the Police, best avoided.

(Double post, accidentally, ignore)