John

One of the good features about the Interstellarum Deep Sky Atlas (not an app but a book !) is that it has a clever system of indicating the visibility of the targets shown on the maps. It's not cheap but it is one of the best out there. This is from the FLO description:

"...It is an innovative, practical tool to choose and find stars, star clusters, nebulae and galaxies. Usually, deep sky objects are shown with just a standard symbol in the star charts. This atlas is different: all objects are shown according to their actual visibility. Four main visibility classes separate out objects that can be seen through 4-, 8- and 12-inch telescopes. Within each visibility class, the objects are labeled in different type weights and using graduated shades and colors for the symbols - the bolder the label or the darker the symbol, the easier it is to see the object...."

https://www.firstlightoptics.com/books/interstellarum-deep-sky-atlas-desk-edition.html

The challenge is (which the above addresses) is that the stated magnitude figures are not always a reliable guide to whether an object is easy or difficult to see. Face on galaxies such as M101 and M33 are classic examples of this.

3 minutes ago, markse68 said:

Hi Magnus, your attention to detail and maths are admirable but shouldn’t/doesn’t the mirror mount in your scope have the adjustments necessary to get the offsets right once mounted?

The offset on many scopes is "built in" by offsetting the position that the secondary is attached to the mounting boss. So Magnus is replicating the approach that Skywatcher and others use.

3 hours ago, PeterW said:

... some challenges are not worth the effort though...

 

You could say that about many of the more difficult astro targets I think. After all most are no more than just another faint pinpoint of light, a vague patch of fuzzy light or a very subtle contrast difference.

Most non-astronomers would wonder why we bother with such things

I suppose its the same in most hobbies though - a hole in one at golf, a fish close to the record in angling, a rare bird or plant spotted. The possibility of such things keeps people trying I reckon

I'm out with my 130mm frac but clouds meant that I missed that occultation.

I'm right on the edge of a cloud layer tonight. It is shifting very slowly in the right direction (ie: more clear sky showing) but its a slow process.

I'm no imager (or NV user) but I understand that the HH is not particularly difficult to image. It's just darn hard to see visually without electronic assistance.

Still, if it was easy then it wouldn't be a challenge, would it ?

If it is the original, non-GOTO version of the HEQ5 then the motors and the control board need to be upgraded as well to make it GOTO, not just the handset.

Here is a photo of the scope with the extension tube in place (from the First Light Optics website):

As above. The eyepiece should be fully inserted and the scope should have an extension tube supplied which needs to be in place for eyepieces to come to focus. I have seen this issue mentioned somewhere else recently with regard to the Bresser dobsonians.

28 minutes ago, Solar B said:

....currently using a 

TV 32mm plossl and I'm not getting on with it .....

 

 

 

 

They have such a lot of eye relief that I found that I needed to add a TV eye cup extender to position my eye correctly and consistently to get the best out of the TV 32mm plossl.

The only thing I would say is don't let the pondering of the theory get in the way of developing practical experience

I get a little lost by some of the optical and physics theory if I'm honest about it. I feel much more comfortable when I get behind a scope and getting on with the practical business of trying to see things.

5 minutes ago, miguel87 said:

My problem is that I have always been a 'why' person. It's not good enough if it works, I want to know WHY and HOW it works 😬

Fair enough. I think quite a few on the forum have a similar approach, and why not ?

When I was testing the SLV 6mm for the forum a few years back I compared it extensively with the Baader Genuine Ortho 6mm which FLO had loaned me for the purposes. Over several sessions I could see no differences at all in the performance of these two excellent eyepieces. With the additional eye relief of the SLV and it's larger eye lens it was more relaxing to use so I would have happily chosen it over the ortho on that occasion. I was rather taken aback by the SLV 6mm as I posted at the time:

On 04/05/2020 at 14:41, RyHead said:

Thank you very much John. The scope and mount are up for £450 locally, so looks like a decent price for the kit. Being able to add the goto is something I'd like to do but not straight away. Good to know i can do it though.

I tend to agree with Cosmic Geoff here, that is quite expensive. Used gear goes for around 60%of the new cost so I would be trying to get that for about £100 less than that.

Great report Doug !

I love zoom eyepieces for double splitting

I have my 130mm refractor out cooling just now so I will visit Bootes if it stays clear.

Despite all the useful information, formulae etc, etc, I've found that there is no substitute for trying things for yourself to see what works best for you under your skies.

Thank goodness for the used astro equipment market !

This is Tele Vue's take on some of these issues. Myth #2 is relevant:

http://www.televue.com/engine/TV3b_page.asp?id=86

I compared the Baader 32mm Classic Plossl with the Vixen NPL 30mm. I slightly preferred the Vixen. I did not use them for solar observing though.

Just now, miguel87 said:

This assumes that some of Jupiter's light exists outside the image of the planet, which I dont think makes sense.

Image a 7mm diameter, circular camera sensor with the exit pupil being projected onto it. If the outer ring of pixels were removed, the image of Jupiter in the middle would not get any dimmer.

Have a look at Don Pensack's post above.

18 minutes ago, markse68 said:

What determines the afov  then? The angle of the focused light cone?

The diameter of the field stop inside the eyepiece coupled with the focal length of the eyepiece define the AFoV. It can be as wide as the internal diameter of the eyepiece barrel but is frequently less because the optical quality of the lenses and overall optical system of the eyepiece would not support acceptable definition over their whole diameter.

Exit pupil is calculated by dividing focal length of the eyepiece by the focal ratio of the scope. Apparrent field of view (AFoV) is not part of the calculation.

Where AFoV does come into play is to determine the amount of sky (true field) that will be visible.

With a very wide AFoV eyepiece, it is possible to have:

- reasonably high magnification

- see a good size chunk of sky

- maintain an exit pupil that is really effective

The above are some of the key reasons that ultra and hyper wide angle eyepieces are popular and effective with fast focal ratio scopes.

Many UHC and O-III filters have a very similar band pass width so deliver very similar performance.

The higher performing ones (which also cost more) have a slightly narrower band pass width with sharper cut offs outside of the permitted band widths. These attributes lead to them delivering more contrast enhancement with receptive nebulae.

Some of the lower cost O-III's are actually closer to a UHC in terms of band pass and performance and equally some UHC's are almost broadband in what they permit.

Astronomik have recently started to manufacture the new range of Tele Vue Bandmate 2 filters which are developing a reputation as about the best currently available. At a cost of course !

Agreed - best not to discuss taxation / import policies on here

It will not affect performance but will affect re-sale value and you paid for a scope that should not have that defect and that's what you should get.

So you have done the right thing and I hope your supplier reacts positively.

25 minutes ago, mikeDnight said:

So the two eyepieces you have will give you 35X and 56X respectively. A 2X SW Delux barlow would be a worthwhile addition I think, and would give you 70X and 112X.  It would also be good for any other scope you may advance to in the future. 

I agree - the Skywatcher Deluxe 2x barlow would be a sensible choice. It is pretty decent quality for it's cost as well. This one is the same I think:

https://www.firstlightoptics.com/barlows/astro-essentials-125-2x-barlow-with-t-thread.html

3 hours ago, Barry-W-Fenner said:

John, what power did you get them close shots at? The detail is amazing! Very clear and crisp. What type of scope is an ED120?

 

 

I use a 7.2 - 21.5 zoom eyepiece with the mobile phone held over the top of it in a very cheap clamp affair (which is pretty rubbish to be honest but it just about does the job). I "zoom" the image on the mobile a bit so it's difficult to say exactly what magnification is actually being used.

Its about the simplest form of astrophotography so I can cope with that !