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westmarch

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Posts posted by westmarch

    Street lighting issues

    in Getting Started With Imaging

    Posted

    Contact your local authority and ask for a shield to be put on the street lamp. If necessary, tell them it is intruding into a bedroom. I had one fitted within the week.  Alternatively, make a local shield - a tarp nailed between two wooden uprights - you put it up when you are observing. Finally, get a long hood to wear - a bit like this.

    John

    • Like 2

    EQ Platform Adjustment

    in Discussions - Mounts

    Posted · Edited by westmarch

    14 hours ago, Mr Spock said:

    My EQ platform tracks pretty well. Other than that new motor I fitted which is erratic (I'm putting the old one back on tomorrow).

    However, I do find I have to, when pointing West, lift the scope up every now and then. I assume because the previous owner was at a different latitude and it was set for there. I'm guessing as that was south of here I'll have to lower the South of the platform to tilt the scope up a little. Is that correct?

    This is probably going to be trial and error as I've no clue how to measure it.

    Hi Michael,

    I suspect you and Peter are correct, you will have to correct the height of the south bearing. If the platform is level, and you wish to correct for a more Northerly latitude, you will need to depress the southern bearing height. 

    If you start by incrementally raising the northern bearings with plywood packers, you will get an idea of the amount of South bearing shimming needed. 

    Alternatively, you can just incorporate the Northern bearing packers into your set up. 

    Just remember your design is optimised  for a different latitude, it will always be somewhat of a comprise  and the bigger the difference in latitude, the bigger the compromise  

    John

    • Like 1

    What did you see tonight?

    in Observing - Reports

    Posted

    Superb session last night - cloudless, slight wind to keep off the dew and moonless - a perfect galaxy session. Went up to the N York Moors at Sutton Bank and set up the 10” dob by 9pm.  When star hopping, I tend to use a 40mm plossl as a seeker and found that a 15mm Explore Scientific EP consistently gave me the best resolution and contrast in this Bortle 4 sky.

    There were a few DSOs I specifically wanted to do having missed out on previous sessions.

    Antennae Galaxies  NGC 4038 and 4039 - by the time I had set up these were frustratingly just edging down into the tree line.

    M61 - struggled with this but it was entering the Vale of York light pollution arc. Picked out in averted vision.

    NGC 4526 - lovely oval galaxy nicely framed in a crux of surrounding stars.

    M85 - Nice elliptical galaxy, easily found with the bonus of adjacent NGC 4394 popping into view in averted vision.

    M64 - oval galaxy with dark irregular patches - intriguing.  I spent a fair bit of time trying to tease out detail.

    M49 - brightly nucleated  oval galaxy.

    NGC 4565 - classic edge on, needle profile with central bulge and long extended arms.

    I tried and failed on the Whale Galaxy NGC 4631 - this was towards the end of the session and was almost vertically above in a relatively star free zone. Dobs are not the easiest to manoeuvre in this position and I sometimes felt that I was in a lovers embrace with the OTA as I moved from RACI to EP. 

    As I was packing up, I had a chat with a chap who had been taking light readings for the National Park. We both bemoaned the continued presence of a stud stable that had erected all-night floodlights, on gantries, immediately adjacent to the park to protect their racehorses from theft. Despite the Sutton Bank site having dark sky status, there is apparently nothing to prevent this! 🤬

    That apart, a very enjoyable night.

    John

     

    • Like 5

    10” Equatorial Platform for Dummies

    in DIY Astronomer

    Posted

    14 minutes ago, noodlehat said:

    @westmarch @FrankRyanJr many thanks for this guide and both your inputs, its my next project after re doing my dob mount. I just have 2 quick questions: 

    - I have a 12" dob with a 700mm diameter circle base with feet at about 600mm diameter , ive worked out i need to scale the plans 15% for its feet to fit on the top board of the EQ mount, I take it I'm just scaling the timber plans and not scaling the aluminium arcs etc? The 50mm gap between boards stays the same and all rods etc?

    - Also, if my dob base has a fixed setting circle on it, if I begin with it aligned correctly, will the EQ mounts movement keep the setting circle aligned correctly or will it all go to hell? Is there any way to get a setting circle on the dob base to work with the movement of an EQ platform?

    Many thanks.

    Hi there,

    your plans for the 12” Dob base sound right to me but my advice to Frank stands: this set of instructions works for up to 10” Dobs, beyond that you need to be careful that your centre of gravity, on full tilt, doesn’t end up outside the base.  If it does, you may have to move the tilt limiting bolts inward on the arcs - reducing the travel. 
     

    For setting circles, the RA is fine but declination is dependent on your telescope base being level. That means you have to put the platform in the mid. position and you half the possible travel when you switch on the motor.  I have setting circles on mine but find them a bit of a faff and rarely use them; relying on Sky Safari and star hopping instead. 

    Good luck with the build. 

    John

    • Like 1

    What did you see tonight?

    in Observing - Reports

    Posted

    41 minutes ago, Mr Spock said:

    Here's when you start to feel really stupid....

    You know my EQ platform not tracking... Well, when I switched it on the other night and it didn't work at all, I actually flipped the N/S switch instead of the On/Off switch. Doh!!!

    It is so easy to do in the dark!  Pointing the south pole of the platform north is another one I have done - that’s a real hassle to correct! 🙄

    John

    Advice needed

    in Getting Started Equipment Help and Advice

    Posted · Edited by westmarch

    Hi there and welcome to the site,

    dew is a perennial problem in our green and pleasant land. Some nights are especially prone to it and the forecast on Clear Outside is a good guide to it. You can find this in the resources menu at the top of the website.  

    You want to cool your scope to reduce heat currents within the scope but when the scope becomes colder than the moisture laden air, dew starts to condense on the scope. 

    In Newtonian scopes, the primary mirror is usually protected by the column of air trapped within the tube it is often the exposed secondary mirror which gets colder first and mists up. The finder scope is also relatively exposed and will cool quickly.

    There are a few things you can do:

    1. When you leave your scope to cool, point it horizontally.  Pointing the mirrors at the deep cold of space is the quickest way to radiate off heat  from the mirrors.

    2. Fit a dew shield. This can be as simple as a foam camping mat around the end of the scope.  If you do a search on dew shields you will see some examples. This extends the column of stable air beyond the secondary mirror and slows heat loss.

    3. You can fit dew heaters - these are electrical heaters which maintain the temperature of the scope a few degrees above dew point but don’t generate distorting heat currents. These can also be fitted to finder scopes.

    4. Keep eyepieces in your pocket when not in use. Since these are some of the most exposed pieces of your optical train, this will keep them warm and help prevent misting.

    5. Use a portable hair dryer on cool setting. This can evaporate dew but its effect is relatively short lived.

    Hope the above helps and don’t become discouraged. Not all nights are dew magnets.

    John

     

    ext 125 oldie indeed

    in Discussions - Scopes / Whole setups

    Inspire me about visual astronomy

    in Getting Started With Observing

    Posted · Edited by westmarch

    You know the satisfaction (or in AP, perhaps the lack of frustration) you get when when every little electronic gizmo and software enhancement works the way it should?

    Finding your target by star hopping or teasing out the observational detail, during a moment of perfect seeing, is similar.  It is like turning up an interesting object with a metal detector, or an angler getting a bite. Sometimes the journey is as interesting as the destination.

    John

    • Like 23

    Jupiter and Mars - visual factors coming together, for once!

    in Observing - Planetary

    Posted

    The weather forecast showed a clear spell this evening between 17:00 and 18:30 and a chance to get in some planetary observation.  My southern aspect sits directly under a streetlight, so normally I never take the dob out there.  I read a thread recently where @vlaiv advocated avoiding dark adaptation with bright planets and using your more densely packed retinal cone receptors to get more detail and, perhaps, some colour vision.

    I think this and some other factors helped me got some of my most detailed views of Jupiter tonight. Using BST Starguider EPs, I found x180 was a bit mushy but at x140 maximised contrast:  the GRS was clearly visible and I was able to distinguish S Polar Region, S and N Equatorial Belts as well as the N Temperate Belt. 

    Mars was subtle, as always, but Syrtis Major Planum and Meridiani Planum were easily distinguishable but I could not pick out the Polar Ice Cap.

    Several other things helped, IMHO:

    1.  Good seeing and transparency.

    2. Relatively high visual altitude

    3. Wind of 10mph - normally this a problem but I think it served to disperse heat shimmer rising from rooftops under the field of view.  Also, by causing an occasional tremor in the FOV, it improved perceptions of detail - a bit like the effect you get when you are struggling to perceive a DSO and the movement from a slight tap on the scope makes it pop into view.

    4. A stable position of the target in the field of view.  In this case, an equatorial platform but any equatorial mount drive allows you the time to exploit moments of good seeing and tease out detail without constantly having to reacquire the target. 

    5. Aperture - this seems to be controversial for planets but having looked through a number of refractors and SCTs, I am convinced that a large aperture scope enhances detail even in bright objects.

    All in all, a very satisfying opportunity snatched before the clouds rolled in.

    John

     

    • Like 12

    Svbony Dew Heater - Anyone Tried?

    in The Astro Lounge

    Posted · Edited by westmarch
    additional link

    17 minutes ago, Ian McCallum said:

    I looked at the 12V dew heaters from FLO, but see that many of the UK made controllers are now unavailable.  I was thinking that it maybe possible to build a controller from scratch, using a suitably rated potentiometer...🤔

    You may find these links helpful.

    https://www.blackwaterskies.co.uk/2013/05/a-cheap-multi-channel-dew-heater-controller/

    https://www.blackwaterskies.co.uk/2013/05/making-your-own-nichrome-dew-heater-bands/

    John

    • Like 1
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