Astro_Nic

Please help! lol

Hi everyone!  Hope you are all well.

I get my 14" OOUK Dobsonian shortly and I'm thinking of adding another upgraded finder to an 80mm version to assist with hunting down faint fuzzies etc.  I am considering the TSFRE80 finder - right angled, 90 degree Amici prism, 1.25" eyepiece attachment.  Got no experience of this setup but hopefully you guys can assist:

• Does anyone have any experience of this model or 80mm finders in general and how do they find them?
• They state that focus is 3-4mm above receptacle and therefore suitable for Kellner or plossl eyepieces.  They suggest their TSIR20 eyepiece - 23 mm illuminated crosshair.  FL of scope is 330mm which will give 14 times mag which should compliment the existing finder.  It has 55 degree FOV.  Are there any better alternatives that will fit? is 55 degree FOV sufficient for a finder? I don't want to over-complicate this.
• They do a 35mm extension tube - would that help increase the choice of crosshair eyepieces?
• They do a 70 degree Erfle - no idea what that is or if it will fit the finder, but that is 20mm so 17x mag but at 70 FOV
• Trying to find another 80mm finder in the UK is almost impossible as nothing is in stock - the Altair version for example has no expected stocking date anywhere.  One alternative is the APM straight through 80mm finder from the same supplier which is 2 inch.  Would all I need to do is add a Amici prism to turn that into a right angled RACI? Does the 2 inch increase my options or is it not necessary in a finder as it is getting more expensive going down this route?

Many thanks for any help you can give in helping me sort an ideal 80mm finder and matching eyepiece.

Stay safe.

Nic

I think maybe it’s a wait and see job - assuming it’s available as an aftermarket option.  Cheers

Now thinking maybe Delos would would be better at that mag - won’t be used as much so paying ethos money for it to sit in a box is maybe not the wisest decision. Sis is coming over from the US shortly so the cost would be c£200 so basically throw away money so can’t lose! 

22 minutes ago, vagk said:

Also Delos 6mm is a good alternative instead of Ethos 6mm and much more comfortable

Will the Delos  cause more drift problems and constant adjustments at that magnification in a dob?  Thanks

4 hours ago, johninderby said:

Never found it a problem with my old OO 14” dob. I did however have OO fit the Baader Steeltrack that I supplied instead of the stock focuser. Also chose a different tube colour..

Wow the scope looks epic in blue!  I enquired about a colour change and they wanted £250....was tempted!  What's all the other electronics you have attached to it?  and where did you get the cart?, light shield and finder?!

2 hours ago, ONIKKINEN said:

I have the VX8, also an aluminum tube. I dont know if people are not entirely honest, if it doesnt affect visual, or i got a weaker than average model but the tube is by far the weakest part of the VX series.

 

Mine is (and always was) noticeably not round. The secondary mirror supports are very weak and have to be tightened quite a bit to be stable. They are tight and it is stable, end of story? Not quite, they have dented the front into a square shape. The rear is aldo dented to a triangular shape because of the 3 point attachment of the mirror cell to the tube walls. The denting means diffraction spikes are not symmetrical because the tube is not round, but other than that just cosmetic damage.

 

For what its worth i have never noticed these in visual use.

Sorry your scope isn't perfect....makes me think maybe it does need some extra support....but £450 for a piece of steel? 

OK so I finally made my initial purchases for my 14" 1,600 FL f4.6 OO dob:

• 9mm APM XWA 100 degree
• 13mm Ethos
• 22mm Nagler
• Paracorr 2
• UHC Astonomik filter
• OIII Astronomik filter
• Zebralight H502pr red head torch
• Some cleaning solution/brushes/clothes etc

Wife is looking at an eyepiece for Xmas for me....I will of course try out the ones I've got once OO have built my scope, but do you think I am more likely to use a higher or lower FL eyepiece?  I do want some great views of the moon and planets, as well as whatever DSO I can glimpse.  Was thinking either 31mm Nagler or 6mm Ethos (I think the 4.7mm might be too much magnification).  The 31mm would give an exit pupil of 5.9 - not sure if that is too much for Bortle 5/6 in terms of contrast.  It would be (with the Paracorr) 59x mag.  My current lowest is the 22 Nagler with 84x.  Or I could get the 6mm Ethos for planetary stuff with mag 267x no paracorr or 307x with Paracorr.

Still mulling over a powermate to increase options.

Thanks for all your help!

So in the end, after much deliberation, I ordered the 14" Orion Optics Dobsonian.  As you may know, this comes with a light aluminium tube.  I have read some reports regarding tube flexing with heavy eyepiece loads, but I was wondering if anyone had any first hand experience of this?  I'm sure it will be fine with just a paracorr and an eyepiece etc, but what about binocular use or if I wanted to get into astrophotography - would this potentially cause any issues?

They offer an upgrade to strengthen the tube - a stainless steel part with a radius block inside the tube.  What's a radius block?  However, they want an extra £450 for this.  This seems steep and is as much as a new scope of decent quality!  Do I need it?

Thanks!

Nic

Thanks, I'll check out the filters.

My other main concern was whether to go with the 20mm APM XWA 100 degree or the 22mm Nagler T4 - Most people seem to rave about their 22 NT4 so went with that, but I know the APM has a good following too.

The other issue is whether I need a higher FL eyepiece than 20/22 such as a 30mm APM UFF - some have suggested that the 22 NT4 won't have a large enough FOV at the 83x magnification.  I am concerned with a larger exit pupil giving a brighter background in my Bortle 5ish sky so thought the 22 would be a good compromise. A 30mm would give 59x mag.

Thanks again.

Nic

OK thanks for all your help.  I think I am going to go with the following to start with:

9mm APM XWA

13mm APM XWA

22mm Nagler T4

Paracorr II

Astronomix OIII

Polarising moon filter - suggestions?

Red torch

How does that sound?  Now need to read up on collimation....am clueless! lol

Thanks

On 01/09/2021 at 18:27, Voyager 3 said:

You will be using a Paracorr II / paracorr for the best correction to use with 100° stuff . It adds 1.15× to the FL/ Focal ratio . 

 

So I take the FL as 1878 . 

Here is your spread with 30mm ( UFF )-13mm-9mm-4.75mm( really a 4.75mm approximately and not a 5mm ) . The 30mm can be substituted by the 20mm XWA  , if your site is light polluted . 

62× - 144× - 208× - 395×  . 

As you can see this is a good set until you reach the 9mm . It's a really big jump from 9mm to 4.75mm . 

A 6mm Ethos fits right in at 313× , but the 7mm APM XWA will also be a good step up at 268× . 

Now it looks like 

62× - 144× - 208× - 268× - 395× . 

Basically you may still need to fill the gap between 7mm and 4.7mm but it is down the list . A coma corrector like the paracorr II must be your first purchase . This assumes you already have good collimation tools . 

 

Wow this eyepiece thing is complex!

so I've decided to ditch the 30mm UFF - too large an exit pupil in light polluted skies - so want something in the 20-24 region I think as my lowest - to start with.  So there's the 24mm APM UFF - I assume this would be great without a parracor, or the 24mm Panopticon,or the 22T4 Nagler or the 20mm APM XWA - which I would assume both require a parracor at f4.6?  Although the Nagler is stated as for f5 and above.  Any views on which one to go for?  I really want the wider FOVs in a manual dob if possible.

I was then thinking of a 6mm, 9mm and 13mm to complete an initial set (4.7mm at 340x too much magnification?)  Which of those am I likely to use most?  For varied use - planets, nebulae and DSO?  As I think I will get 1 Ethos and 2 APM 100 XWA.

If I need a parracor I will probably only be able to go for 2 eyepieces initially with the rest at xmas - so the 20mm and which other would give me best bang for buck?  Or if I go for three and no parracor, would you go 6,9,20 or 9,13,20 for example?

Thanks again for all your great advice!

Nic

Thanks.....think the jury is out in all the reviews I've read....half say go UHC and half OIII - only going to start with one for now - maybe flip a coin?!

Wow thanks guys!  But stop spending my money! lol!

I am thinking that the 30mm may have a too large exit pupil and hence be too bright - so looks like a 20mm might be the place to start.

I'm still not sure I understand why not to use a powermate - looks like I can lose two eyepieces then!  Although I get it's a pain to change and also adds weight and length to the eyepiece.....have I just listed the reasons?!  Cheaper though!

Ethos looks the business but I'm not spending that money on my first eyepiece!

Will I ever get the opportunity to use 395x ?  Seems very high......

So do I need a parracor - I do want an awesome view and I am the sort of person to look for problems after spending lots of money!  Type 2?

Have no collimation tools....aaaarrrrggghhh!  What do you recommend?

How do you balance an aluminium dob?  Velcro straps with running wrist weights?  Obviously can't use magnetism and don't want to start drilling into a brand new scope!

Thanks!

I guess the Morpheus could be a good binoviewer choice.  In the 17.5 with x2 barlow?

35 minutes ago, Louis D said:

Written by people who haven't spent a good chunk of their lives out under the stars, I suspect.  I tend to leave mine in the focuser the entire night when I want to use all of my eyepieces at double their normal magnification, which isn't very often.

25x to 50x is good for very large open star clusters, solar system conjunctions, typical solar observing (with safe solar filter) sweeping rich star fields, and detecting comets.

50x to 100x is good for large open star clusters, emission nebula, the whole moon at once, and large galaxies from dark sites.

100x to 150x is good for small open star clusters, planets on nights of average seeing, smaller galaxies from dark sites, viewing the moon in large swaths, and splitting many double star systems.

150x to 200x is good for planets on nights of above average seeing, planetary nebula, lunar details, starting to resolve globular clusters, and splitting tighter double stars.

200x+ is good for planets on nights of exceptional seeing, bright planetary nebula details, challenging lunar details, interacting galaxies from dark sites, fully resolving globular clusters, and splitting the tightest double stars.

I'm sure I missed someone's favorite type of observing in there.  That, and folks will argue about what magnification works best for each.  It's nice to have an assortment of eyepieces to try out to match the seeing conditions with the object at hand.

OIII only pass the two oxygen emission lines while UHC filters add one or both hydrogen emission lines.  As a result, the OIII filter has a narrower passband and a higher rejection of light pollution.  However, some emission nebula just don't emit much in the oxygen lines, so the UHC or even an Hß filter comes into play.

You don't use them together.  It's either one or the other.  The OIII is a subset of the UHC.  The OIII and Hß are mutually exclusive.

A lot of folks like the Baader Contrast Booster on planets and other objects to make it easier to pick out low contrast details, but I've not tried one personally.  I've had some luck with an 80a filter on Jupiter to bring out the Great Red Spot better.

Probably not.  They're heavy and fat.  You might not be able to get two of them close enough together for your IPD.  That, and your nose or at least its bridge between your eyes might not fit between the eyepieces, either.  Most folks use smaller, lighter weight eyepieces in their BVs.  Adapted microscope eyepieces can even work quite well I've found.

Also, most folks tend to use lower powered eyepieces with BVs because it's easier to merge their images.  Higher powered eyepieces tend to reveal any slight miscollimation in the BV.  You can always boost the power by adding a Barlow element ahead of the BV.  They also help you to reach focus in Dobs which don't usually have enough in-focus for BVs natively (about 100mm required).

Thanks very much for your help!

14 hours ago, Louis D said:

Don't overlook the 9mm APM XWA 100°.  It's lighter and cheaper than the ES alternative, and most reports rank it as just as good if not better.

Excellent choice.  My preferred eyepiece at that focal length.  The ES-82 is wider, but has issues with CAEP (Chromatic Aberration of the Exit Pupil) aka, ring of fire at the edge.

You'll find yourself either leaving it in the focuser for extended observing periods or removing it.  PMs and Barlows are just too clunky to be swapping in and out regularly.  I would spend the money on dedicated eyepieces, myself.  That, and you'll have a really long optics train hanging off your focuser.  I would probably recommend 13mm and 4.77mm APM XWA 100° to fill the power gaps instead.  The latter is 110° which will be really helpful at high powers with a nondriven Dob.

Pick up a cheap moon filter off of ebay or similar if you feel the need.

Pick up a quality OIII first and UHC second.  Don't go cheap on either one.  Astronomik, Lumicon, and several others are quite good.

As long as neither of you has astigmatism (CYL correction), you'll both be fine without eyeglasses at the eyepiece.  You can just focus out the distance correction.  Depending on how strong the prescription is, the field stop may get a bit fuzzy because you're moving the image circle away from it to compensate for the observer's eye.

Thanks - will take a look at the APM 9mm

It's weird as all the beginner guides say get barlows to reduce number of eyepieces, yet all the advice seems to be to not to bother......

So say I get all 100 degree APMs - what targets would I use for each of the sizes - 5mm, 9mm, 13mm and 30mm ?  Is that a good spread?  340x, 170x, 123x, 53x ?

What's the main difference between OIII and UHC filters?  Do you use both at once or just one at a time?

Are the APMs suitable for binoviewers if I went that way?  

Thanks!

So I think I'm going to purchase a 14 inch dob - f 4.6, FL 1,600mm, PV 1/10.

Need some eyepieces etc to go with it.  I thought the following might be a good place to start, but open to suggestions of alternatives.  Interest is DSOs but also some planetary, nebula etc:

• 9mm ES 100 degree FOV 2 inch - this would give me 170 x magnification;
• 30mm APM UFF 2 inch - this would give me 53 degree magnification;
• 2x Televue powermate 2 inch - this would then increase the above magnification options to 340, 170, 106 and 53;
• I could replace the the ES with the 9mm Televue Nagler 82 degree FOV as it is a similar price but seems to be much more easily available - how would these two compare?
• I could possible add another ES 82 degree field or similarly priced eyepiece if you feel I need an additional one;
• Moon filter - suggestions please?
• Nebula filter - ES CLS 
• I don't wear glasses.  Wife does but only long sighted so eye relief shouldn't be an issue.

Please could you advise on the above?  

Many thanks!

I don't wear glasses.  However, my wife does and I would like her to occasionally enjoy the views.

4 minutes ago, John said:

With my Orion Optics 12 inch F/5.3 dobsonian (focal length 1600mm) I find that I use eyepieces of the following focal lengths the most:

21mm (76x)

13mm (123x)

8mm (200x

6mm (267x)

4.7mm (340x)

I prefer eyepieces with a very wide angle of view (100 degrees) to maximise drift times of targets in the undriven scope, plus I just like the hyper-wide views

I don't use binoviewers with the scope - if I did I would need to change to eyepieces with smaller fields of view because the hyper-wides would be too fat !

I don't use a coma corrector with my scope but if you go for something that is F/5 or faster (eg: F/4.5) and opt for wide field eyepieces then you may well need to so that coma generated by the scopes mirror does not mar your lovely wide views.

 

If I were to start with two eye pieces, which ones would you recommend?  If I get quality eyepieces I won't be able to get 5!  

Would you recommend a x2 Barlow as well?

Cheers

3 minutes ago, John said:

With my Orion Optics 12 inch F/5.3 dobsonian (focal length 1600mm) I find that I use eyepieces of the following focal lengths the most:

21mm (76x)

13mm (123x)

8mm (200x

6mm (267x)

4.7mm (340x)

I prefer eyepieces with a very wide angle of view (100 degrees) to maximise drift times of targets in the undriven scope, plus I just like the hyper-wide views

I don't use binoviewers with the scope - if I did I would need to change to eyepieces with smaller fields of view because the hyper-wides would be too fat !

I don't use a coma corrector with my scope but if you go for something that is F/5 or faster (eg: F/4.5) and opt for wide field eyepieces then you may well need to so that coma generated by the scopes mirror does not mar your lovely wide views.

 

Thanks John

Yeah I probably need more basic help.....what makes will work with f4.6.....what are good FL of the eyepieces.....what eye relief do I need (not clear what that is!).....what field of view would be best - people have said 'large', but what is large?  Do I need 100 degree or is 80 degree large....etc.....  Thanks everyone!

17 hours ago, ollypenrice said:

Like Mutley earlier on in the thread, I would look into a David Lukehurst Dob.  He has a solid reputation. It can be very instructive to put a maker's name into Google followed by 'customer service...'

You're right to uncouple visual observing from astrophotography because the requirements have astonishingly little in common.

Olly

Thanks, I will take a look.

Now trying to get an idea of eyepieces and binoviewers / barlows / comma correction etc....seems a mine field for a beginner!  Cheers

Firstly thanks for all your helpful comments.  I think I'm going to go for a relatively large dob - looking at the Orion Optics VX range as a compromise.  Size undecided at moment - I'd really like the 14 inch though!  Good suggestion looking out for used scopes, but not sure how often a used OO VX would come up so might have to go down the new route.

Assuming I go with an OO VX, which eyepieces and other equipment would you recommend?  I actually like the idea of a binoviewer as well, so if someone could also suggest a binoviewer and suitable eyepieces as well that would be great.  The OO VX 14 inch is f4.6, FL 1,600.

If I'm getting a decent scope I really want eyepieces that will do it justice, but I also don't want to spend a fortune that I might not appreciate as a beginner.

Thanks again!

Nic

It's always only partially clear - unless it's totally not clear!