Eye piece advise for 300p

[ian2]

13 hours ago, Barry-W-Fenner said:

Hi Ian.

I haven't purchased any new eye pieces yet. I am  quite interested in picking up one in the Morpheus range at some point. I am quite pleased that I decided to hold off for the time being to get some experience with my current eye pieces. Unfortunately that hasn't happened as the weather has been so poor over the last month.

Regards

baz

 

thanks for the update Baz. Yeah the weather has been poor up here also,  in one month I’ve had the scope out once. 😞 

Based on the advice in this thread I’m also considering the Morpheus range. Ideally i would like to try out some eyepieces but since i have only 1 decent eyepiece (32mm) I’ll probably go for a mid focal range Morpheus and take it from there.

cheers

Ian

[Barry-W-Fenner]

7 minutes ago, ian2 said:

thanks for the update Baz. Yeah the weather has been poor up here also,  in one month I’ve had the scope out once. 😞 

Based on the advice in this thread I’m also considering the Morpheus range. Ideally i would like to try out some eyepieces but since i have only 1 decent eyepiece (32mm) I’ll probably go for a mid focal range Morpheus and take it from there.

cheers

Ian

Hi Ian.

I am thinking similar, I would like to purchase something mid focal and hopefully barlow it for more power. That's assuming a Morpheus will play nice with a x2 BST barlow?

Not sure what to go for to be honest. I quite enjoy viewing with my 8mm bst at x187 in the 300p. However the image is not great to be honest. Stars seem to be a bit distorted and mushy. So maybe something along the lines of the 14mm Morpheus and barlow down to 7mm??
Again any advise appreciated

Barry

 

[Barry-W-Fenner]

1 hour ago, bomberbaz said:

Hey Baz, how's it going.

Just a quick one re NeoWise. It is currently becoming visible slightly to the NW and moves accross to the NE later on passing North at around 1pm.

You will only see it if you can get a view that gives you the bottom 10 degrees of altitude. For me this means looking from a bedroom window to gain the height above my neighbours roofs which thankfully are on a slight gradient below me so gains me a couple of feet and allows me to see it throughout the night. Hope that makes sense.

Hi Steve.

all Good thanks matey. Hope you are keeping safe and well.

Thanks for the heads up regarding the comet. I have Ursa major at my north West becoming visible around 11pm
will it be visible near this? If so I will try to hunt it down.

I am not having a great time with the bsts unfortunately. The 8mm, 12mm and 15mm seem to perform OK on planets, however stara are not good, main stars are still displaying quite blurry and look slightly unfocused, the back ground stars are also very faint through the focuser, almost barely visible. If I look through the finderscope they are very clear.

I have collimated the scope with my short cheshire  and it seems spot on. All 3 primary clips visible evenly and the dot in the donut so I'm happy with that. I just don't think the bsts and 300p0like playing together. I'm now looking to purchase a mid power Morpheus and barlow it for now.

Cheers baz

 

 

Edited July 12, 2020 by Barry-W-Fenner

[bomberbaz]

 

That's Neowise at 23.20 tonight according to stellarium. Capella makes a good guide to finding it, if you can see capella, you can see the comet. 

A morpheus 14 and barlow ( I prefer telecentric ones such as ES focal extender) would be a great addition to your scope. 

Strange about the stars still looking quite fuzzy, is this even in the centre?

[bomberbaz]

BTW, what about this for a bargain 👍😅

https://www.rothervalleyoptics.co.uk/baader-morpheus-eyepiece-set-6-eps.html

[ian2]

2 hours ago, Barry-W-Fenner said:

Hi Ian.

I am thinking similar, I would like to purchase something mid focal and hopefully barlow it for more power. That's assuming a Morpheus will play nice with a x2 BST barlow?

Not sure what to go for to be honest. I quite enjoy viewing with my 8mm bst at x187 in the 300p. However the image is not great to be honest. Stars seem to be a bit distorted and mushy. So maybe something along the lines of the 14mm Morpheus and barlow down to 7mm??
Again any advise appreciated

Barry

 

i did consider getting a star guider as an interim measure, but sounds like that wouldn’t be a good idea. Apart from my celestron omni 32mm i have old 0.95” eyepieces from my 60mm tasco refractor. Would a barlow have to be 2” to work well with the Morpheus eyepieces?

 

wife is off for 2 weeks holidays do I can’t do anything but after that I have some annual leave coming up and during that time i’ll be able to intercept any dodgy looking packages and dispose of incriminating evidence such as receipts 😇

Edited July 12, 2020 by ian2

[John]

I find it odd that the mid range BST Starguiders are not working that well in the 300mm F/5 dob.

I've used those myself in my 12 inch F/5.3 dob and found them really rather good. The 8mm compared well to my 8mm Ethos for example with sharp stars, nice dark background sky etc, etc.

The 25mm is not so good with stars in the outer 30% of the field of view showing astigmatism but the 18mm, 12mm and 8mm were eyepieces that I was quite impressed with in my dob.

Dare I suggest that the collimation might be worth a check ?

 

[bomberbaz]

what mirrors are you using @John, could you have better quality mirror giving a superior view?  Don't even know if that is a possibility but just curious.

[Barry-W-Fenner]

3 hours ago, John said:

I find it odd that the mid range BST Starguiders are not working that well in the 300mm F/5 dob.

I've used those myself in my 12 inch F/5.3 dob and found them really rather good. The 8mm compared well to my 8mm Ethos for example with sharp stars, nice dark background sky etc, etc.

The 25mm is not so good with stars in the outer 30% of the field of view showing astigmatism but the 18mm, 12mm and 8mm were eyepieces that I was quite impressed with in my dob.

Dare I suggest that the collimation might be worth a check ?

 

All suggestions welcome John, I'm a bit proplexed as to why my views are not particularly good.

I purchased a short cheshire and the Baader click lock a couple of weeks ago, part of my reasoning for purchasing the click lock was to make sure the cheshire was central.

two of the 3 primary clips were showing clearly but the 3rd was minimal. I tweeked the secondary via my collimation knobs and got the 3 clips even. There was no actual loosining and moving of the secondary, just a slight adjustment on the screws. The primary was then quite far out, maybe 1cm from the dot to the ring in the primary. I got this lined up perfectly and put the scope away for the best part of two weeks 😕

I have used it the last couple of nights and stars are definitely not the bright points of light that they should be. Back ground stars are very dim/faint. Main stars like vega look like they would if you was slightly out of focus by a small amount, a bit blurry and not sharp at all. I will try to get a pic if I can tonight.

I will also run through the collimation process again to see if anything needs changing

Thank you

Baz

[John]

35 minutes ago, bomberbaz said:

what mirrors are you using @John, could you have better quality mirror giving a superior view?  Don't even know if that is a possibility but just curious.

OO with a .987 strehl but I've had some great views with Skywatcher mirrors as well.

[John]

21 minutes ago, Barry-W-Fenner said:

All suggestions welcome John, I'm a bit proplexed as to why my views are not particularly good.

I purchased a short cheshire and the Baader click lock a couple of weeks ago, part of my reasoning for purchasing the click lock was to make sure the cheshire was central.

two of the 3 primary clips were showing clearly but the 3rd was minimal. I tweeked the secondary via my collimation knobs and got the 3 clips even. There was no actual loosining and moving of the secondary, just a slight adjustment on the screws. The primary was then quite far out, maybe 1cm from the dot to the ring in the primary. I got this lined up perfectly and put the scope away for the best part of two weeks 😕

I have used it the last couple of nights and stars are definitely not the bright points of light that they should be. Back ground stars are very dim/faint. Main stars like vega look like they would if you was slightly out of focus by a small amount, a bit blurry and not sharp at all. I will try to get a pic if I can tonight.

I will also run through the collimation process again to see if anything needs changing

Thank you

Baz

Just have a go at a basic star test on Polaris at around 250x. Rack though sharp focus and see if the image looks pretty much the same either side as the diffraction rings expand around what should be a fairly central dark secondary shadow.

 

[Barry-W-Fenner]

Just remembered that I took a couple of pics of Mars in the early hours of Saturday, One of them I have attached.

 

Please forgive the rather poor shot of Mars itself, The reason I have attached the pic is to show how poor the the two white "points of light" are, This is pretty much how most brighter stars show at focus.  Quite blurred and out of focus. from memory this was while I was using my 12mm BST

To contradict myself, Mars looked excellent, as mentioned in @Johnobserving thread a very clear gibbous phase,  Red in colour with the striking southern polar cap visible.  Jupiter & Saturn also looked probably the best I have seen them.  The Cats eye blew me away and the detail in the moon this morning at 6am against a bright blue sky was spectacular!

I will re-check collimation shortly and do as suggested above on Polaris to see if I can get a better understanding of whats going on.

 

Thanks all

Baz

 

 

 

 

 

[Ricochet]

1 hour ago, Barry-W-Fenner said:

two of the 3 primary clips were showing clearly but the 3rd was minimal. I tweeked the secondary via my collimation knobs and got the 3 clips even. There was no actual loosining and moving of the secondary, just a slight adjustment on the screws. The primary was then quite far out, maybe 1cm from the dot to the ring in the primary.

Does your Cheshire have crosshairs at the bottom? If it does, do those crosshairs line up with the doughnut on the primary however you rotate the Cheshire? 

[Barry-W-Fenner]

1 minute ago, Ricochet said:

Does your Cheshire have crosshairs at the bottom? If it does, do those crosshairs line up with the doughnut on the primary however you rotate the Cheshire? 

it does have a crosshair at the bottom. when I go out I will fully rotate the cheshire and see if the crosshair stays central.

Thank you

[Don Pensack]

The alignment of the crosshairs on the primary center marker, if a coma corrector is not used, has a very loose tolerance of about 0.03D, where D = mirror diameter in mm.

Essentially, if the crosshairs are anywhere on the center marker, you're probably OK.

It is the primary collimation that has tighter tolerances: 0.005 f/r³,which, fortunately is seen with 2X magnification by the typical Cheshire, so, if the scope is an f/5, for example,

the primary alignment tolerance is 0.625mm, but the read of the tool need only be better than 1.25mm, or about 1/10 the diameter of the primary center marker if the primary center marker is 1/2" across.

That is a pretty easy "read" in the tool IF the center marker is close to the same size as the black center in the Cheshire.

 

Collimation has two main components: mechanical and optical.  And when you are learning collimation, the one to pay attention to is the optical alignment.

So don't worry whether the primary is centered under the focuser, or whether the 3 clips are equally visible, unless you are concerning yourself with the mechanical collimation of the scope.

It is the optical collimation (tilt of secondary and primary) that truly determine the quality of the images you see.

 

If you have paid attention to optical collimation and still have poor images, remember the 3 "C"s:

Collimation (which you've just taken care of), Cooling (any mirror larger than 6" will need 1-3 hours before it is cooled to the ambient temperature and will yield sharp high power images).  And Conditions,

which includes the seeing, the darkness, and the transparency of the air (with seeing the most important for sharp star images).  Only if all 3 are good will you see good star images above about 20x/inch of aperture.

Edited July 13, 2020 by Don Pensack

[bomberbaz]

Don makes a very good point there Baz, how long have you been allowing for cooling before viewing, an uncooled ota could be the reason for mushy views at high magnfication whle you get seemingly clear views through the spotter which cools quickly due to its size. 

[Barry-W-Fenner]

15 hours ago, Don Pensack said:

The alignment of the crosshairs on the primary center marker, if a coma corrector is not used, has a very loose tolerance of about 0.03D, where D = mirror diameter in mm.

Essentially, if the crosshairs are anywhere on the center marker, you're probably OK.

It is the primary collimation that has tighter tolerances: 0.005 f/r³,which, fortunately is seen with 2X magnification by the typical Cheshire, so, if the scope is an f/5, for example,

the primary alignment tolerance is 0.625mm, but the read of the tool need only be better than 1.25mm, or about 1/10 the diameter of the primary center marker if the primary center marker is 1/2" across.

That is a pretty easy "read" in the tool IF the center marker is close to the same size as the black center in the Cheshire.

 

Collimation has two main components: mechanical and optical.  And when you are learning collimation, the one to pay attention to is the optical alignment.

So don't worry whether the primary is centered under the focuser, or whether the 3 clips are equally visible, unless you are concerning yourself with the mechanical collimation of the scope.

It is the optical collimation (tilt of secondary and primary) that truly determine the quality of the images you see.

 

If you have paid attention to optical collimation and still have poor images, remember the 3 "C"s:

Collimation (which you've just taken care of), Cooling (any mirror larger than 6" will need 1-3 hours before it is cooled to the ambient temperature and will yield sharp high power images).  And Conditions,

which includes the seeing, the darkness, and the transparency of the air (with seeing the most important for sharp star images).  Only if all 3 are good will you see good star images about about 20x/inch of aperture.

Hi Don,

Thanks for the insightful post regarding the primary mirror, It would seem that you have forgotten more about mirrors than I will ever know 🙂 As you in the optics profession?

So it would appear that i have collimated to a mechanical state by going over the usual processes. How would one know how to collimate to a optical state?

Reference the 3 Cs I think the scope was out for about an hour on each occasion cooling. Perhaps i am not giving the scope the required amount of time to cool down enough. It might explain why the moon looked great at 6am as I left the scope out from my 3am viewing session.

Thanks for your assistance, Much appreciated.

Baz

 

[Barry-W-Fenner]

4 hours ago, bomberbaz said:

Don makes a very good point there Baz, how long have you been allowing for cooling before viewing, an uncooled ota could be the reason for mushy views at high magnfication whle you get seemingly clear views through the spotter which cools quickly due to its size. 

Hi Steve,

@Don Pensack Does have a valid point there regarding my cooling times, As mentioned above I have been giving the mirror around an hours cooling time before use but this might not be sufficient. I will try to set up the scope around 8pm going forward. This should give a couple of hours cooling before use.

Out of interest, Do you all cool your dobs with the covers obviously off and at a horizontal position, Or say 45 degrees.

I keep my dobs in the utility room out back so thought they would be closer to outside temperature from the outset, However that may not be the case.

I shall report back when I get some viewing in!

Thanks Steve

[bomberbaz]

I thhink most cool their dobs in the horizontal position with covers off. 

Regarding early morning moon clarity the air tends to be more settled very early morning so often gives better seeing. 

There could be many reasons why your views are suffering as you claim, you will get to the bottom of it though. 

I went through something like this once with my 12" flex tube a few years back, mine was mainly collimation I am slightly ashamed to say. 

Steve

Edited July 13, 2020 by bomberbaz

[Louis D]

2 hours ago, Barry-W-Fenner said:

Out of interest, Do you all cool your dobs with the covers obviously off and at a horizontal position, Or say 45 degrees.

I cool mine straight up and down like a chimney.  I don't know what advantage tilting it would provide.

[bomberbaz]

38 minutes ago, Louis D said:

I cool mine straight up and down like a chimney.  I don't know what advantage tilting it would provide.

Helps keep your mrrors cleaner longer louis

[John]

I cool mine at around 45 degree angle with all the caps off.

Takes 30-40 minutes before I can use high powers to full effect. Low to medium powers can be used more or less straight out of the house.

 

[Barry-W-Fenner]

Doesn't look like there will be any viewing tonight as it's all cloud here. Might set the Dob up in the utility room and double check the collimation later. 🤔

[bomberbaz]

14 minutes ago, Barry-W-Fenner said:

Doesn't look like there will be any viewing tonight as it's all cloud here. Might set the Dob up in the utility room and double check the collimation later. 🤔

Post up a picture taken through the focuser tube, let us have a look. A 2nd eye looking things over may see thing your maybe over looking. Just a suggestion.

[Louis D]

2 hours ago, bomberbaz said:

Helps keep your mrrors cleaner longer louis

I just avoid going out on nights with significant particulate matter in the air, like on night of the 4th of July (fireworks residue), when my neighbors are burning logs in their fireplaces, backyard grilling, or are running their smokers overnight.  The rest of the time, the level of airborne particulates hasn't been much of an issue for me.